app-forensics/aflplusplus: ensure flags work for both GCC and Clang

Clang gets invoked during the build, so make sure we strip out flags
which don't work for it too.

Signed-off-by: Sam James <sam@gentoo.org>

app-forensics/aflplusplus/aflplusplus-4.32c.ebuild

@@ -79,6 +79,9 @@ src_compile() {
 	# bug #945258
 	append-cflags -std=gnu17
 
+	strip-unsupported-flags
+	CC=clang CXX=clang++ strip-unsupported-flags
+
 	mymake
 }