Allow overriding tools/bazel path with BAZELISK_WRAPPER_PATH (#567)

In some projects the tools/bazel path isn't practical. This allows
users to override this path with the BAZELISK_WRAPPER_PATH env var /
.bazeliskrc config option.

core/core.go

@@ -33,10 +33,11 @@ import (
 )
 
 const (
-	bazelReal      = "BAZEL_REAL"
-	skipWrapperEnv = "BAZELISK_SKIP_WRAPPER"
-	wrapperPath    = "./tools/bazel"
-	maxDirLength   = 255
+	bazelReal               = "BAZEL_REAL"
+	skipWrapperEnv          = "BAZELISK_SKIP_WRAPPER"
+	defaultWrapperDirectory = "./tools"
+	defaultWrapperName      = "bazel"
+	maxDirLength            = 255
 )
 
 var (
@@ -502,6 +503,13 @@ func maybeDelegateToWrapperFromDir(bazel string, wd string, config config.Config
 		return bazel
 	}
 
+	wrapperPath := config.Get("BAZELISK_WRAPPER_DIRECTORY")
+	if wrapperPath == "" {
+		wrapperPath = filepath.Join(defaultWrapperDirectory, defaultWrapperName)
+	} else {
+		wrapperPath = filepath.Join(wrapperPath, defaultWrapperName)
+	}
+
 	root := ws.FindWorkspaceRoot(wd)
 	wrapper := filepath.Join(root, wrapperPath)
 	if stat, err := os.Stat(wrapper); err == nil && !stat.Mode().IsDir() && stat.Mode().Perm()&0111 != 0 {