Allow overriding binaries installed by hack/go-install.sh

Makefile targets for binary dependencies (i.e. code-generator,
openshift-goimports and golangci-lint) now use version-less
filepaths:

    `$(TOOLS_DIR)/<Binary>` instead of `$(TOOLS_DIR)/<Binary>-<Version>`

`$(TOOLS_DIR)/<Binary>` may be a symlink to the versioned executable file.

Secondly, hack/go-install.sh now adds a check for `$(TOOLS_DIR)/<Binary>`
to be present and executable, in which case it skips `go install` invocation.

This allows for making local changes to these dependencies (e.g. when working
on kcp-dev/code-generator) and generating client code.

On-behalf-of: SAP robert.vasek@sap.com
Signed-off-by: Robert Vasek <robert.vasek@clyso.com>

Author: gman0

Makefile

@@ -25,15 +25,15 @@ TMPDIR := $(shell mktemp -d)
 
 CODE_GENERATOR_VER := v2.3.0
 CODE_GENERATOR_BIN := code-generator
-CODE_GENERATOR := $(TOOLS_DIR)/$(CODE_GENERATOR_BIN)-$(CODE_GENERATOR_VER)
+CODE_GENERATOR := $(TOOLS_DIR)/$(CODE_GENERATOR_BIN)
 export CODE_GENERATOR # so hack scripts can use it
 
 $(CODE_GENERATOR):
 	GOBIN=$(TOOLS_GOBIN_DIR) $(GO_INSTALL) github.com/kcp-dev/code-generator/v2 $(CODE_GENERATOR_BIN) $(CODE_GENERATOR_VER)
 
 OPENSHIFT_GOIMPORTS_VER := c70783e636f2213cac683f6865d88c5edace3157
 OPENSHIFT_GOIMPORTS_BIN := openshift-goimports
-OPENSHIFT_GOIMPORTS := $(TOOLS_DIR)/$(OPENSHIFT_GOIMPORTS_BIN)-$(OPENSHIFT_GOIMPORTS_VER)
+OPENSHIFT_GOIMPORTS := $(TOOLS_DIR)/$(OPENSHIFT_GOIMPORTS_BIN)
 export OPENSHIFT_GOIMPORTS # so hack scripts can use it
 
 $(OPENSHIFT_GOIMPORTS):
@@ -45,7 +45,7 @@ imports: $(OPENSHIFT_GOIMPORTS)
 
 GOLANGCI_LINT_VER := v1.58.1
 GOLANGCI_LINT_BIN := golangci-lint
-GOLANGCI_LINT := $(TOOLS_DIR)/$(GOLANGCI_LINT_BIN)-$(GOLANGCI_LINT_VER)
+GOLANGCI_LINT := $(TOOLS_DIR)/$(GOLANGCI_LINT_BIN)
 
 $(GOLANGCI_LINT):
 	GOBIN=$(TOOLS_GOBIN_DIR) $(GO_INSTALL) github.com/golangci/golangci-lint/cmd/golangci-lint $(GOLANGCI_LINT_BIN) $(GOLANGCI_LINT_VER)

hack/go-install.sh

@@ -41,6 +41,9 @@ if [ -z "${GOBIN}" ]; then
   exit 1
 fi
 
+# An executable already exists, exit early.
+[[ -f "${GOBIN}/${2}" && -x $(realpath "${GOBIN}/${2}") ]] && exit 0
+
 rm -f "${GOBIN}/${2}"* || true
 
 # install the golang module specified as the first argument