Update build of toolchain/sysroot to not touch installation root

This changes everything to ensure that only the `install` step actually
tries to install things. Everything is staged into temporary `./install`
folders inside of the build directory and then running the build
system's `install` target will actually copy out everything using CMake
builtins.

Closes #442

cmake/wasi-sdk-sysroot.cmake

@@ -10,7 +10,8 @@ find_program(MAKE make REQUIRED)
 option(WASI_SDK_DEBUG_PREFIX_MAP "Pass `-fdebug-prefix-map` for built artifacts" ON)
 option(WASI_SDK_INCLUDE_TESTS "Whether or not to build tests by default" OFF)
 
-set(wasi_sysroot ${CMAKE_INSTALL_PREFIX}/share/wasi-sysroot)
+set(wasi_tmp_install ${CMAKE_CURRENT_BINARY_DIR}/install)
+set(wasi_sysroot ${wasi_tmp_install}/share/wasi-sysroot)
 
 if(WASI_SDK_DEBUG_PREFIX_MAP)
   add_compile_options(
@@ -44,7 +45,7 @@ endif()
 # compiler-rt build logic
 # =============================================================================
 
-set(compiler_rt_dst ${CMAKE_INSTALL_PREFIX}/lib/clang/${clang_version})
+set(compiler_rt_dst ${wasi_tmp_install}/lib/clang/${clang_version})
 ExternalProject_Add(compiler-rt-build
   SOURCE_DIR "${llvm_proj_dir}/compiler-rt"
   CMAKE_ARGS
@@ -234,6 +235,10 @@ endforeach()
 # misc build logic
 # =============================================================================
 
+install(DIRECTORY ${wasi_tmp_install}/lib ${wasi_tmp_install}/share
+        USE_SOURCE_PERMISSIONS
+        DESTINATION ${CMAKE_INSTALL_PREFIX})
+
 # Add a top-level `build` target as well as `build-$target` targets.
 add_custom_target(build ALL)
 foreach(target IN LISTS WASI_SDK_TARGETS)
@@ -244,14 +249,13 @@ endforeach()
 
 # Install a `VERSION` file in the output prefix with a dump of version
 # information.
-set(version_file_tmp ${CMAKE_CURRENT_BINARY_DIR}/VERSION)
+set(version_file_tmp ${wasi_tmp_install}/VERSION)
 execute_process(
   COMMAND ${PYTHON} ${version_script} dump
   WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   OUTPUT_FILE ${version_file_tmp})
-install(
-  FILES ${version_file_tmp}
-  DESTINATION ${CMAKE_INSTALL_PREFIX})
+install(FILES ${wasi_tmp_install}/VERSION
+        DESTINATION ${CMAKE_INSTALL_PREFIX})
 
 if(WASI_SDK_INCLUDE_TESTS)
   add_subdirectory(tests)
@@ -264,13 +268,13 @@ set(dist_dir ${CMAKE_CURRENT_BINARY_DIR}/dist)
 # Tarball with just `compiler-rt` builtins within it
 wasi_sdk_add_tarball(dist-compiler-rt
   ${dist_dir}/libclang_rt.builtins-wasm32-wasi-${wasi_sdk_version}.tar.gz
-  ${CMAKE_INSTALL_PREFIX}/lib/clang/${clang_version}/lib/wasi)
+  ${wasi_tmp_install}/lib/clang/${clang_version}/lib/wasi)
 add_dependencies(dist-compiler-rt compiler-rt)
 
 # Tarball with the whole sysroot
 wasi_sdk_add_tarball(dist-sysroot
   ${dist_dir}/wasi-sysroot-${wasi_sdk_version}.tar.gz
-  ${CMAKE_INSTALL_PREFIX}/share/wasi-sysroot)
+  ${wasi_tmp_install}/share/wasi-sysroot)
 add_dependencies(dist-sysroot build install)
 
 add_custom_target(dist DEPENDS dist-compiler-rt dist-sysroot)

cmake/wasi-sdk-toolchain.cmake

@@ -7,6 +7,8 @@ set(WASI_SDK_ARTIFACT "" CACHE STRING "Name of the wasi-sdk artifact being produ
 
 string(REGEX REPLACE "[ ]+" ";" llvm_cmake_flags_list "${LLVM_CMAKE_FLAGS}")
 
+set(wasi_tmp_install ${CMAKE_CURRENT_BINARY_DIR}/install)
+
 if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE MinSizeRel)
 endif()
@@ -16,7 +18,7 @@ set(default_cmake_args
   -DCMAKE_AR=${CMAKE_AR}
   -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
   -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX})
+  -DCMAKE_INSTALL_PREFIX=${wasi_tmp_install})
 
 if(CMAKE_C_COMPILER_LAUNCHER)
   list(APPEND default_cmake_args -DCMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER})
@@ -106,6 +108,14 @@ ExternalProject_Add(llvm-build
   USES_TERMINAL_INSTALL ON
 )
 
+add_custom_target(build ALL DEPENDS llvm-build)
+
+# Installation target for this outer project for installing the toolchain to the
+# system.
+install(DIRECTORY ${wasi_tmp_install}/bin ${wasi_tmp_install}/lib ${wasi_tmp_install}/share
+        USE_SOURCE_PERMISSIONS
+        DESTINATION ${CMAKE_INSTALL_PREFIX})
+
 # Build logic for `wasm-component-ld` installed from Rust code.
 set(wasm_component_ld_root ${CMAKE_CURRENT_BINARY_DIR}/wasm-component-ld)
 set(wasm_component_ld ${wasm_component_ld_root}/bin/wasm-component-ld${CMAKE_EXECUTABLE_SUFFIX})
@@ -118,24 +128,34 @@ add_custom_command(
   COMMAND
     cargo install --root ${wasm_component_ld_root} ${rust_target_flag}
       wasm-component-ld@${wasm_component_ld_version}
+  COMMAND
+    cmake -E make_directory ${wasi_tmp_install}/bin
+  COMMAND
+    cmake -E copy ${wasm_component_ld} ${wasi_tmp_install}/bin
   COMMENT "Building `wasm-component-ld` ...")
-
-add_custom_target(wasm-component-ld ALL DEPENDS ${wasm_component_ld})
-
-install(
-  PROGRAMS ${wasm_component_ld}
-  DESTINATION ${CMAKE_INSTALL_PREFIX}/bin)
+add_custom_target(wasm-component-ld DEPENDS ${wasm_component_ld})
+add_dependencies(build wasm-component-ld)
 
 # Setup installation logic for CMake support files.
-install(
-  PROGRAMS src/config/config.sub src/config/config.guess
-  DESTINATION ${CMAKE_INSTALL_PREFIX}/share/misc)
-install(
-  FILES wasi-sdk.cmake wasi-sdk-pthread.cmake wasi-sdk-p2.cmake
-  DESTINATION ${CMAKE_INSTALL_PREFIX}/share/cmake)
-install(
-  DIRECTORY cmake/Platform
-  DESTINATION ${CMAKE_INSTALL_PREFIX}/share/cmake)
+add_custom_target(misc-files)
+add_dependencies(build misc-files)
+
+function(copy_misc_file src dst_folder)
+  cmake_path(GET src FILENAME src_filename)
+  set(dst ${wasi_tmp_install}/share/${dst_folder}/${src_filename})
+  add_custom_command(
+    OUTPUT ${dst}
+    COMMAND cmake -E copy ${CMAKE_CURRENT_SOURCE_DIR}/${src} ${dst})
+  add_custom_target(copy-${src_filename} DEPENDS ${dst})
+  add_dependencies(misc-files copy-${src_filename})
+endfunction()
+
+copy_misc_file(src/config/config.sub misc)
+copy_misc_file(src/config/config.guess misc)
+copy_misc_file(wasi-sdk.cmake cmake)
+copy_misc_file(wasi-sdk-pthread.cmake cmake)
+copy_misc_file(wasi-sdk-p2.cmake cmake)
+copy_misc_file(cmake/Platform/WASI.cmake cmake/Platform)
 
 include(wasi-sdk-dist)
 
@@ -156,6 +176,6 @@ endif()
 set(dist_dir ${CMAKE_CURRENT_BINARY_DIR}/dist)
 wasi_sdk_add_tarball(dist-toolchain
   ${dist_dir}/wasi-toolchain-${wasi_sdk_version}-${wasi_sdk_artifact}.tar.gz
-  ${CMAKE_INSTALL_PREFIX})
-add_dependencies(dist-toolchain llvm-build install)
+  ${wasi_tmp_install})
+add_dependencies(dist-toolchain build)
 add_custom_target(dist DEPENDS dist-toolchain)