package/go: fix go-bootstrap when parent dir contains invalid .git

Building host-go within docker fails:

error obtaining VCS status: exit status 128
	Use -buildvcs=false to disable VCS stamping.

Reproduction of the issue:

mkdir go-issue-61620
cd ./go-issue-61620
wget https://go.dev/dl/go1.19.11.src.tar.gz
mkdir go-bootstrap
tar -xf go1.19.11.src.tar.gz -C ./go-bootstrap --strip-components=1
cd ./go-bootstrap/src/
bash make.bash
cd ../../
wget https://go.dev/dl/go1.20.6.src.tar.gz
mkdir go
tar -xf go1.20.6.src.tar.gz -C ./go/ --strip-components=1
printf "gitdir: ../../does/not/exist/.git" > ./.git
cd ./go/src/
GOROOT_BOOTSTRAP=$(pwd)/../../go-bootstrap/ bash make.bash

The error only occurs when the .git that git detects in the parent directory of
the GOROOT_BOOTSTRAP is invalid or not present causing errors when running `git`
commands within GOROOT_BOOTSTRAP.

Report: https://lists.buildroot.org/pipermail/buildroot/2023-July/671344.html
Fixes: https://gitlab.com/buildroot.org/buildroot/-/jobs/4725186525
Upstream issue: golang/go#61620
Upstream PR: golang/go#61621

Signed-off-by: Christian Stewart <christian@aperture.us>

---

v1 -> v2:

 - sort HOST_GO_MAKE_ENV alphabetically
 - simplify the patch to set buildvcs=false unconditionally for go-bootstrap
 - create a minimal reproduction of the issue
 - simplify the commit message with the minimal reproduction

v2 -> v3:

 - drop unnecessary go.mk change

package/go/0002-cmd-dist-set-buildvcs-false-when-building-go-bootstr.patch

@@ -0,0 +1,73 @@
+From 6b05378097c6a386ed9912d2471976dc39504e86 Mon Sep 17 00:00:00 2001
+From: Christian Stewart <christian@aperture.us>
+Date: Thu, 27 Jul 2023 21:28:47 -0700
+Subject: [PATCH] cmd/dist: set buildvcs=false when building go-bootstrap
+
+When building go-bootstrap as part of the make.bash process, the cmd/dist
+invokes the bootstrap Go compiler to build the go_bootstrap tool:
+
+${GOROOT_BOOTSTRAP}/bin/go install -tags=math_big_pure_go compiler_bootstrap purego bootstrap/cmd/...
+
+If there is an invalid .git directory in a parent of ${GOROOT_BOOTSTRAP},
+make.bash will fail. Reproduction of the issue:
+
+ mkdir go-issue-61620
+ cd ./go-issue-61620
+ wget https://go.dev/dl/go1.19.11.src.tar.gz
+ mkdir go-bootstrap
+ tar -xf go1.19.11.src.tar.gz -C ./go-bootstrap --strip-components=1
+ cd ./go-bootstrap/src/
+ bash make.bash
+ cd ../../
+ wget https://go.dev/dl/go1.20.6.src.tar.gz
+ mkdir go
+ tar -xf go1.20.6.src.tar.gz -C ./go/ --strip-components=1
+ printf "gitdir: ../../does/not/exist/.git" > ./.git
+ cd ./go/src/
+ GOROOT_BOOTSTRAP=$(pwd)/../../go-bootstrap/ bash make.bash
+
+The build fails with the following error:
+
+ Building Go toolchain1 using [snip]/go-1.19.10.
+ error obtaining VCS status: exit status 128
+ Use -buildvcs=false to disable VCS stamping.
+ go tool dist: FAILED: [snip]/go-1.19.10/bin/go install -tags=math_big_pure_go \
+ compiler_bootstrap purego bootstrap/cmd/...: exit status 1
+
+This change unconditionally sets -buildvcs=false when compiling go-bootstrap. We
+don't need the revision information in those binaries anyway. Setting this flag
+was previously not done as we were unsure if the go-bootstrap compiler would be
+new enough to support the buildvcs build flag. Since Go 1.20.x, Go 1.19.x is the
+minimum version for go-bootstrap, and supports -buildvcs=false. We can now set
+-buildvcs=false without worrying about compatibility.
+
+Related: https://github.com/golang/go/issues/54852
+Fixes: https://github.com/golang/go/issues/61620
+
+---
+
+Upstream PR: https://github.com/golang/go/pull/61621
+
+Signed-off-by: Christian Stewart <christian@aperture.us>
+
+---
+ src/cmd/dist/buildtool.go | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/src/cmd/dist/buildtool.go b/src/cmd/dist/buildtool.go
+index a528d7aa76..3b411d6ebb 100644
+--- a/src/cmd/dist/buildtool.go
++++ b/src/cmd/dist/buildtool.go
+@@ -221,6 +221,9 @@ func bootstrapBuildTools() {
+ cmd := []string{
+ pathf("%s/bin/go", goroot_bootstrap),
+ "install",
++ // Fixes cases where an invalid .git is present in a parent of GOROOT_BOOTSTRAP.
++ // See: https://github.com/golang/go/issues/61620
++ "-buildvcs=false",
+ "-tags=math_big_pure_go compiler_bootstrap purego",
+ }
+ if vflag > 0 {
+-- 
+2.41.0
+