cmd/link: don't reset variable size when handling -X flag
The linker's -X flag allows setting/changing a string variable's
content at link time. Currently it resets its size then write a
new string header pointing to the new content. This mostly works.
But under ASAN build the string variable can have larger size
than the usual 2 words, due to the red zone. Resetting the size
can cause the variable to "overlap" (in ASAN's view) with other
variables. Don't reset the size.
Fixes #56175.
Change-Id: Ib364208201a7a2fd7f44f9b1797834198736a405
Reviewed-on: https://go-review.googlesource.com/c/go/+/442635
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com> Reviewed-by: Than McIntosh <thanm@google.com>