cmd/cgo/internal/testsanitizers: for "leak", use -fsanitize=address
We currently test the leak detector by running "go build -asan",
which will pass -fsanitize=address to the C compiler.
So use that when testing whether the option works.
Fixes #72128
Change-Id: I4efc0b689bfda04c80dbac30a5c757215f297d2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/655535 Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
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