CI: add the grabpl build-backend command into the repo (#52673)

* Move the grabpl build-backend command and clean it up a bit

pkg/build/compilers/install.go

@@ -0,0 +1,50 @@
+package compilers
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+const (
+	ArmV6        = "/opt/rpi-tools/arm-bcm2708/arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc"
+	Armv7        = "arm-linux-gnueabihf-gcc"
+	Armv7Musl    = "/tmp/arm-linux-musleabihf-cross/bin/arm-linux-musleabihf-gcc"
+	Arm64        = "aarch64-linux-gnu-gcc"
+	Arm64Musl    = "/tmp/aarch64-linux-musl-cross/bin/aarch64-linux-musl-gcc"
+	Osx64        = "/tmp/osxcross/target/bin/o64-clang"
+	Win64        = "x86_64-w64-mingw32-gcc"
+	LinuxX64     = "/tmp/x86_64-centos6-linux-gnu/bin/x86_64-centos6-linux-gnu-gcc"
+	LinuxX64Musl = "/tmp/x86_64-linux-musl-cross/bin/x86_64-linux-musl-gcc"
+)
+
+func Install() error {
+	// From the os.TempDir documentation:
+	// On Unix systems, it returns $TMPDIR if non-empty,
+	// else /tmp. On Windows, it uses GetTempPath,
+	// returning the first non-empty value from %TMP%, %TEMP%, %USERPROFILE%,
+	// or the Windows directory. On Plan 9, it returns /tmp.
+	tmp := os.TempDir()
+
+	var (
+		centosArchive = "x86_64-centos6-linux-gnu.tar.xz"
+		osxArchive    = "osxcross.tar.xz"
+	)
+
+	for _, fname := range []string{centosArchive, osxArchive} {
+		path := filepath.Join(tmp, fname)
+		if _, err := os.Stat(path); err != nil {
+			return fmt.Errorf("stat error: %w", err)
+		}
+		// Ignore gosec G204 as this function is only used in the build process.
+		//nolint:gosec
+		cmd := exec.Command("tar", "xfJ", fname)
+		cmd.Dir = tmp
+		if output, err := cmd.CombinedOutput(); err != nil {
+			return fmt.Errorf("failed to unpack %q: %q, %w", fname, output, err)
+		}
+	}
+
+	return nil
+}