Limit [[nodiscard]] to clang

GCC 7.4 has problems with combining [[nodiscard]] with
__attribute__((visibility(""))). Disable as there's enough compilation
coverage for clang to find issues.

Bug: v8:11707
Change-Id: I9e61463c4d11dbc3b03d458e2810206fb93de108
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2854737Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74262}

include/v8config.h

@@ -336,7 +336,10 @@ path. Add it with -I<path> to the command line
 # define V8_HAS_ATTRIBUTE_UNUSED 1
 # define V8_HAS_ATTRIBUTE_VISIBILITY 1
 # define V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT (!V8_CC_INTEL)
-# define V8_HAS_CPP_ATTRIBUTE_NODISCARD (V8_HAS_CPP_ATTRIBUTE(nodiscard))
+
+// [[nodiscard]] does not work together with with
+// __attribute__((visibility(""))) on GCC 7.4 which is why there is no define
+// for V8_HAS_CPP_ATTRIBUTE_NODISCARD. See https://crbug.com/v8/11707.
 
 # define V8_HAS_BUILTIN_ASSUME_ALIGNED 1
 # define V8_HAS_BUILTIN_CLZ 1