Fix crypt.cpp sanitizer test on FreeBSD

FreeBSD doesn't provide a crypt.h header but instead defines the functions
in unistd.h. Use __has_include() to handle that case.

Reviewed By: #sanitizers, vitalybuka

Differential Revision: https://reviews.llvm.org/D85406

compiler-rt/test/sanitizer_common/TestCases/Posix/crypt.cpp

@@ -6,7 +6,9 @@
 #include <assert.h>
 #include <unistd.h>
 #include <cstring>
+#if __has_include(<crypt.h>)
 #include <crypt.h>
+#endif
 
 int
 main (int argc, char** argv)