[newlib-cygwin] gcc: quiet Wattribute for no_sanitize("address")

[Sebastian Huber <sh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=b9af5041bd5662748e060d7b716c18a224d91254

commit b9af5041bd5662748e060d7b716c18a224d91254
Author: rlibby <rlibby@FreeBSD.org>
Date:   Sat Dec 21 02:43:20 2019 +0000

    gcc: quiet Wattribute for no_sanitize("address")
    
    This is an unfortunate instance where the __has_attribute check does
    not function usefully.  Gcc does have the attribute, but for gcc it only
    applies to functions, not variables, and trying to apply it to a
    variable generates Wattribute.  So far we only apply the attribute to
    variables.  Only enable the attribute for clang, for now.
    
    Reviewed by:    Anton Rang <rang at acm.org>
    Sponsored by:   Dell EMC Isilon
    Differential Revision:  https://reviews.freebsd.org/D22875

Diff:
---
 newlib/libc/include/sys/cdefs.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
index 1f2ce063d..1be994ffd 100644
--- a/newlib/libc/include/sys/cdefs.h
+++ b/newlib/libc/include/sys/cdefs.h
@@ -709,8 +709,12 @@
 /* Function should not be analyzed. */
 #define	__no_lock_analysis	__lock_annotate(no_thread_safety_analysis)
 
-/* Function or variable should not be sanitized, ie. by AddressSanitizer */
-#if __has_attribute(no_sanitize)
+/*
+ * Function or variable should not be sanitized, i.e. by AddressSanitizer.
+ * GCC has the nosanitize attribute, but as a function attribute only, and
+ * warns on use as a variable attribute.
+ */
+#if __has_attribute(no_sanitize) && defined(__clang__)
 #define __nosanitizeaddress	__attribute__((no_sanitize("address")))
 #else
 #define __nosanitizeaddress