tree cf5b7dc0ed2ac2c55a949962d19416bae8553809
parent f4f929a48d358acb206a6cbc91dfdee813c45aed
author Josh Bleecher Snyder <josharian@gmail.com> 1748021397 +0000
committer Josh Bleecher Snyder <josharian@gmail.com> 1748025007 -0700

dockerimg: mount Go caches for faster Docker race builds

When building sketch binary with race detector in Docker, the system
was downloading all modules and rebuilding from scratch every time,
making repeated builds slow and inefficient.

This adds host Go cache mounting to buildLinuxSketchBinWithDocker by:
- Getting host GOCACHE and GOMODCACHE directories using 'go env'
- Mounting them as volumes in the Docker container:
  -v $GOCACHE:/root/.cache/go-build
  -v $GOMODCACHE:/go/pkg/mod

The optimization ensures:
- First race build: Downloads modules (same time as before)
- Subsequent race builds: Reuses cached modules (much faster)
- Build artifacts persist between Docker container runs

Adds helper functions getHostGoCacheDir() and getHostGoModCacheDir()
to retrieve cache paths from the host environment, with proper error
handling and path validation.

Includes unit test to verify cache directory detection works correctly
on all platforms where Go is installed.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: sd279e56e1574e4e1k