[compiler-rt] [test] [profile] Mark the without-libc test as unsupported on mingw

Mingw toolchains always end up referencing the malloc symbol due to
the CRT startup files.

Differential Revision: https://reviews.llvm.org/D148166

compiler-rt/test/profile/instrprof-without-libc.c

@@ -9,6 +9,9 @@
 // an MSVC environment, so we can't make this test portable.
 // UNSUPPORTED: target={{.*msvc.*}}
 
+// The MinGW CRT init files do reference malloc etc, so this test fails.
+// UNSUPPORTED: target={{.*windows-gnu.*}}
+
 #include <stdint.h>
 #include <stdlib.h>