use GO_LDFLAGS instead of LDFLAGS to prevent inheriting unrelated options

[thaJeztah]

relates to docker/docker-ce-packaging#666

When building on Fedora 36, the build failed. I suspect this is because the
rpm tools also set LDFLAGS, but with options that cannot be used;

GO_LINKMODE=dynamic
+ ./scripts/build/binary
  /go/src/github.com/docker/cli ~/rpmbuild/BUILD/src
  Building dynamic docker-linux-arm64
  + go build -o build/docker-linux-arm64 -tags ' pkcs11' -ldflags '-Wl,-z,relro -Wl,--as-needed  -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -Wl,--build-id=sha1 -Wl,-dT,/root/rpmbuild/BUILD/src/.package_note-docker-ce-cli-0.0.0.20220330082637.68cad50-0.fc36.aarch64.ld -w -X "github.com/docker/cli/cli/version.GitCommit=68cad50" -X "github.com/docker/cli/cli/version.BuildTime=2022-03-30T20:05:36Z" -X "github.com/docker/cli/cli/version.Version=0.0.0-20220330082637-68cad50" -X "github.com/docker/cli/cli/version.PlatformName=Docker Engine - Community"' -buildmode=pie github.com/docker/cli/cmd/docker
# github.com/docker/cli/cmd/docker
flag provided but not defined: -Wl,-z,relro
usage: link [options] main.o

This patch changes the variable we use to GO_LDFLAGS, taking a similar approach
as containerd, and various other projects using this name: https://grep.app/search?q=GO_LDFLAGS

Signed-off-by: Sebastiaan van Stijn github@gone.nl

- What I did

- How I did it

- How to verify it

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Merging #3513 (391e6ad) into master (68cad50) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3513   +/-   ##
=======================================
  Coverage   59.00%   59.00%           
=======================================
  Files         284      284           
  Lines       23839    23839           
=======================================
  Hits        14066    14066           
  Misses       8914     8914           
  Partials      859      859           

[crazy-max]

Indeed we call ./scripts/build/binary directly on docker-ce-packaging so we are not sandboxed unfortunately.

[thaJeztah]

Right, so I think moby/moby resets LDFLAGS at the start (would have to double check), so that would avoid the problem as well, but I was thinking that "have a GO_LDFLAGS allows people to (if needed for anything) set an initial set of flags (before our scripts add the options we set), which could be useful.