Fix aarch64 build with GCC

GCC does not have __has_feature, so writing #if __has_feature(foo),
without a guard, will cause GCC to error. This is tripping the gRPC
update.

Prior to https://boringssl-review.googlesource.com/c/boringssl/+/60765,
this worked because the preamble to every assembly file would define the
missing __has_feature macro as part of detecting MSan. Now we pick up
the logic in <openssl/base.h>, which tries not to stomp over symbols we
don't own. This had the side effect of removing the __has_feature
polyfill.

Though "public", <openssl/asm_base.h> is not really a public header, so
we could put the __has_feature polyfill in there. But we already have a
pattern for detecting sanitizers in <openssl/target.h>, so just switch
to that one.

Change-Id: I747b4513f1b2f189d2df629149f22fd0fa490257
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/61565
Commit-Queue: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

crypto/chacha/asm/chacha-armv8.pl

@@ -142,7 +142,7 @@ $code.=<<___;
 ChaCha20_ctr32:
 	AARCH64_VALID_CALL_TARGET
 	cbz	$len,.Labort
-#if __has_feature(hwaddress_sanitizer) && __clang_major__ >= 10
+#if defined(OPENSSL_HWASAN) && __clang_major__ >= 10
 	adrp	@x[0],:pg_hi21_nc:OPENSSL_armcap_P
 #else
 	adrp	@x[0],:pg_hi21:OPENSSL_armcap_P

crypto/fipsmodule/sha/asm/sha1-armv8.pl

@@ -183,7 +183,7 @@ $code.=<<___;
 sha1_block_data_order:
 	// Armv8.3-A PAuth: even though x30 is pushed to stack it is not popped later.
 	AARCH64_VALID_CALL_TARGET
-#if __has_feature(hwaddress_sanitizer) && __clang_major__ >= 10
+#if defined(OPENSSL_HWASAN) && __clang_major__ >= 10
 	adrp	x16,:pg_hi21_nc:OPENSSL_armcap_P
 #else
 	adrp	x16,:pg_hi21:OPENSSL_armcap_P

crypto/fipsmodule/sha/asm/sha512-armv8.pl

@@ -187,7 +187,7 @@ $code.=<<___;
 $func:
 	AARCH64_VALID_CALL_TARGET
 #ifndef	__KERNEL__
-#if __has_feature(hwaddress_sanitizer) && __clang_major__ >= 10
+#if defined(OPENSSL_HWASAN) && __clang_major__ >= 10
 	adrp	x16,:pg_hi21_nc:OPENSSL_armcap_P
 #else
 	adrp	x16,:pg_hi21:OPENSSL_armcap_P

include/openssl/target.h

@@ -139,6 +139,9 @@
 #define OPENSSL_MSAN
 #define OPENSSL_ASM_INCOMPATIBLE
 #endif
+#if __has_feature(hwaddress_sanitizer)
+#define OPENSSL_HWASAN
+#endif
 #endif
 
 #if defined(OPENSSL_ASM_INCOMPATIBLE)