diff --git a/Makefile b/Makefile
index 89eee63..426df1d 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,7 @@ build/compiler-rt.BUILT: build/llvm.BUILT build/wasi-libc.BUILT
 	# Do the build, and install it.
 	mkdir -p build/compiler-rt
 	cd build/compiler-rt && cmake -G Ninja \
+		-DCMAKE_SYSROOT=$(BUILD_PREFIX)/share/wasi-sysroot \
 		-DCMAKE_C_COMPILER_WORKS=ON \
 		-DCMAKE_CXX_COMPILER_WORKS=ON \
 		-DCMAKE_AR=$(BUILD_PREFIX)/bin/ar \
@@ -112,7 +113,7 @@ build/compiler-rt.BUILT: build/llvm.BUILT build/wasi-libc.BUILT
 		-DCOMPILER_RT_ENABLE_IOS=OFF \
 		-DCOMPILER_RT_DEFAULT_TARGET_ONLY=On \
 		-DWASI_SDK_PREFIX=$(BUILD_PREFIX) \
-		-DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP) --sysroot=$(BUILD_PREFIX)/share/wasi-sysroot" \
+		-DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP)" \
 		-DLLVM_CONFIG_PATH=$(ROOT_DIR)/build/llvm/bin/llvm-config \
 		-DCOMPILER_RT_OS_DIR=wasi \
 		-DCMAKE_INSTALL_PREFIX=$(PREFIX)/lib/clang/$(CLANG_VERSION)/ \
@@ -154,10 +155,11 @@ build/libcxx.BUILT: build/llvm.BUILT build/compiler-rt.BUILT build/wasi-libc.BUI
 	# Do the build.
 	mkdir -p build/libcxx
 	cd build/libcxx && cmake -G Ninja $(LIBCXX_CMAKE_FLAGS) \
-	    -DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP) --sysroot=$(BUILD_PREFIX)/share/wasi-sysroot" \
-	    -DCMAKE_CXX_FLAGS="$(DEBUG_PREFIX_MAP) --sysroot=$(BUILD_PREFIX)/share/wasi-sysroot" \
-	    -DLIBCXX_LIBDIR_SUFFIX=$(ESCAPE_SLASH)/wasm32-wasi \
-	    $(LLVM_PROJ_DIR)/libcxx
+		-DCMAKE_SYSROOT=$(BUILD_PREFIX)/share/wasi-sysroot \
+		-DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP) \
+		-DCMAKE_CXX_FLAGS="$(DEBUG_PREFIX_MAP) \
+		-DLIBCXX_LIBDIR_SUFFIX=$(ESCAPE_SLASH)/wasm32-wasi \
+		$(LLVM_PROJ_DIR)/libcxx
 	ninja $(NINJA_FLAGS) -v -C build/libcxx
 	# Do the install.
 	DESTDIR=$(DESTDIR) ninja $(NINJA_FLAGS) -v -C build/libcxx install
@@ -195,10 +197,11 @@ build/libcxxabi.BUILT: build/libcxx.BUILT build/llvm.BUILT
 	# Do the build.
 	mkdir -p build/libcxxabi
 	cd build/libcxxabi && cmake -G Ninja $(LIBCXXABI_CMAKE_FLAGS) \
-	    -DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP) --sysroot=$(BUILD_PREFIX)/share/wasi-sysroot" \
-	    -DCMAKE_CXX_FLAGS="$(DEBUG_PREFIX_MAP) --sysroot=$(BUILD_PREFIX)/share/wasi-sysroot" \
-	    -DLIBCXXABI_LIBDIR_SUFFIX=$(ESCAPE_SLASH)/wasm32-wasi \
-	    $(LLVM_PROJ_DIR)/libcxxabi
+		-DCMAKE_SYSROOT=$(BUILD_PREFIX)/share/wasi-sysroot \
+		-DCMAKE_C_FLAGS="$(DEBUG_PREFIX_MAP) \
+		-DCMAKE_CXX_FLAGS="$(DEBUG_PREFIX_MAP) \
+		-DLIBCXXABI_LIBDIR_SUFFIX=$(ESCAPE_SLASH)/wasm32-wasi \
+		$(LLVM_PROJ_DIR)/libcxxabi
 	ninja $(NINJA_FLAGS) -v -C build/libcxxabi
 	# Do the install.
 	DESTDIR=$(DESTDIR) ninja $(NINJA_FLAGS) -v -C build/libcxxabi install