Add several tests to test printf of various configurations.

wasi-libc builds special versions of printf and other routines optimized
for the case where long double and floating-point in general are not
needed. Ensure that everything still compiles and runs.

tests/compile-only/printf-long-double.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+volatile long double x = 42.0L;
+
+int main(void) {
+    printf("the answer is %Lf\n", x);
+    return 0;
+}

tests/general/printf-long-double-enabled.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+volatile long double x = 42.0L;
+
+int main(void) {
+    printf("the answer is %Lf\n", x);
+    return 0;
+}

tests/general/printf-long-double-enabled.c.options

@@ -0,0 +1 @@
+-lc-printscan-long-double

tests/general/printf-long-double-enabled.c.stdout.expected

@@ -0,0 +1 @@
+the answer is 42.000000

tests/general/printf-no-float.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+volatile int x = 42;
+
+int main(void) {
+    printf("the answer is %d\n", x);
+    return 0;
+}

tests/general/printf-no-float.c.stdout.expected

@@ -0,0 +1 @@
+the answer is 42

tests/general/printf-no-long-double.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+volatile double x = 42.0;
+
+int main(void) {
+    printf("the answer is %f\n", x);
+    return 0;
+}

tests/general/printf-no-long-double.c.stdout.expected

@@ -0,0 +1 @@
+the answer is 42.000000