golang: Move build cache into $(TMP_DIR)

This changes the default build cache directory from $(TOPDIR)/.go-build
to $(TMP_DIR)/go-build, so that the cache directory is ignored by git
and is removed by "make dirclean".

This does not move/remove a build cache directory in the previous
location; it will need to be removed manually.

Fixes https://github.com/openwrt/packages/issues/13675.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/golang/golang-values.mk

@@ -236,7 +236,7 @@ endif
 
 # General build info
 
-GO_BUILD_CACHE_DIR:=$(or $(call qstrip,$(CONFIG_GOLANG_BUILD_CACHE_DIR)),$(TOPDIR)/.go-build)
+GO_BUILD_CACHE_DIR:=$(or $(call qstrip,$(CONFIG_GOLANG_BUILD_CACHE_DIR)),$(TMP_DIR)/go-build)
 GO_MOD_CACHE_DIR:=$(DL_DIR)/go-mod-cache
 
 GO_MOD_ARGS= \

lang/golang/golang/Config.in

@@ -17,7 +17,7 @@ config GOLANG_BUILD_CACHE_DIR
 	default ""
 	help
 	  Store the Go build cache in this directory.
-	  If not set, uses './.go-build'.
+	  If not set, uses '$(TMP_DIR)/go-build'.
 
 config GOLANG_MOD_CACHE_WORLD_READABLE
 	bool "Ensure Go module cache is world-readable"