gc.c: move ASAN check to configure

Availability of attributes are checked in configure these days,
rather than compiler macros.  Also
__attribute__((no_address_safety_analysis)) is considered
deprecated in both GCC and Clang.  Use the current best practice
if available.  See also:

https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
https://clang.llvm.org/docs/AddressSanitizer.html


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65558 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/m4/ruby_decl_attribute.m4

@@ -29,6 +29,7 @@ ${rbcv_cond+[@%:@define ]attrib[](attrib_params)[ x]}
 ${rbcv_cond+[@%:@endif]})
 $6
 @%:@define mesg ("")
+@%:@define san "address"
     attrib[](attrib_params)[;], [],
     [rbcv="$mac"; break])
 done