Move gitSha1 build time variable from main to goenv package

Moving and exporting this variable from the main to the goenv package
allows us to use it from both the main and the builder package.
This is done in preparation to include the value in `tinygo build`
linker flags, so that we can embed the version and git sha into binaries
built with tinygo.

Makefile

@@ -208,7 +208,7 @@ lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a:
 # Build the Go compiler.
 tinygo:
 	@if [ ! -f "$(LLVM_BUILDDIR)/bin/llvm-config" ]; then echo "Fetch and build LLVM first by running:"; echo "  make llvm-source"; echo "  make $(LLVM_BUILDDIR)"; exit 1; fi
-	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) build -buildmode exe -o build/tinygo$(EXE) -tags byollvm -ldflags="-X main.gitSha1=`git rev-parse --short HEAD`" .
+	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) build -buildmode exe -o build/tinygo$(EXE) -tags byollvm -ldflags="-X github.com/tinygo-org/tinygo/goenv.GitSha1=`git rev-parse --short HEAD`" .
 
 test: wasi-libc
 	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) test $(GOTESTFLAGS) -timeout=20m -buildmode exe -tags byollvm ./builder ./cgo ./compileopts ./compiler ./interp ./transform .

goenv/version.go

@@ -14,6 +14,12 @@ import (
 // Update this value before release of new version of software.
 const Version = "0.23.0-dev"
 
+var (
+	// This variable is set at build time using -ldflags parameters.
+	// See: https://stackoverflow.com/a/11355611
+	GitSha1 string
+)
+
 // GetGorootVersion returns the major and minor version for a given GOROOT path.
 // If the goroot cannot be determined, (0, 0) is returned.
 func GetGorootVersion(goroot string) (major, minor int, err error) {

main.go

@@ -36,12 +36,6 @@ import (
 	"go.bug.st/serial/enumerator"
 )
 
-var (
-	// This variable is set at build time using -ldflags parameters.
-	// See: https://stackoverflow.com/a/11355611
-	gitSha1 string
-)
-
 // commandError is an error type to wrap os/exec.Command errors. This provides
 // some more information regarding what went wrong while running a command.
 type commandError struct {
@@ -1023,8 +1017,8 @@ func getBMPPorts() (gdbPort, uartPort string, err error) {
 
 func usage(command string) {
 	version := goenv.Version
-	if strings.HasSuffix(version, "-dev") && gitSha1 != "" {
-		version += "-" + gitSha1
+	if strings.HasSuffix(version, "-dev") && goenv.GitSha1 != "" {
+		version += "-" + goenv.GitSha1
 	}
 
 	switch command {
@@ -1620,8 +1614,8 @@ func main() {
 			goversion = s
 		}
 		version := goenv.Version
-		if strings.HasSuffix(goenv.Version, "-dev") && gitSha1 != "" {
-			version += "-" + gitSha1
+		if strings.HasSuffix(goenv.Version, "-dev") && goenv.GitSha1 != "" {
+			version += "-" + goenv.GitSha1
 		}
 		fmt.Printf("tinygo version %s %s/%s (using go version %s and LLVM version %s)\n", version, runtime.GOOS, runtime.GOARCH, goversion, llvm.Version)
 	case "env":