fuzzer: fix unused setting on argc & argv

At some point the compiler changed to not propagate argument attributes
from the prototype to the definition.  Add a hacky macro to insert it
by default instead to avoid need for (void) casts.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
(cherry picked from commit 6508649486444d20636d1ff15df7db7302f3c46c)
Signed-off-by: Sam James <sam@gentoo.org>

dumpelf.c

@@ -579,8 +579,6 @@ static void parseargs(int argc, char *argv[])
 #if PAX_UTILS_LIBFUZZ
 int LLVMFuzzerInitialize(int *argc, char ***argv)
 {
-	(void)argc;
-	(void)argv;
 	(void)parseargs;
 	security_init(false);
 	return 0;

fuzz-ar.c

@@ -15,9 +15,6 @@ static int fd;
 
 int LLVMFuzzerInitialize(int *argc, char ***argv)
 {
-	(void)argc;
-	(void)argv;
-
 	fd = memfd_create("fuzz-input.a", MFD_CLOEXEC);
 	if (fd == -1)
 		errp("memfd_create() failed");

paxinc.h

@@ -112,9 +112,14 @@ const char *strfileperms(const char *fname);
 #define PTR_ALIGN_DOWN(base, size) ((__typeof__(base))ALIGN_DOWN((uintptr_t)(base), (size)))
 #define PTR_ALIGN_UP(base, size)   ((__typeof__(base))ALIGN_UP  ((uintptr_t)(base), (size)))
 
-/* Support for libFuzzer: https://llvm.org/docs/LibFuzzer.html */
+/*
+ * Support for libFuzzer: https://llvm.org/docs/LibFuzzer.html
+ * No headers define this API, so we have to do it ourselves.
+ */
 #if PAX_UTILS_LIBFUZZ
-int LLVMFuzzerInitialize(__unused__ int *argc, __unused__ char ***argv);
+int LLVMFuzzerInitialize(int *argc, char ***argv);
+/* Attributes on the prototype are ignored, so hack the definition. */
+#define LLVMFuzzerInitialize(c, v) LLVMFuzzerInitialize(__unused__ c, __unused__ v)
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
 #endif