package/go: Build host tools with host CC

The go build system doesn't have the notion of cross compiling, but just the
notion of architecture.  When the host and target architectures are different
it expects to be given a target cross compiler in CC_FOR_TARGET.  When the
architectures are the same it will use CC_FOR_TARGET for both host and target
compilation.  To work around this limitation build and install a set of
compiler and tool binaries built with CC_FOR_TARGET set to the host compiler.
Also, the go build system is not compatible with ccache, so use
HOSTCC_NOCCACHE.  See https://github.com/golang/go/issues/11685.

Fixes build errors like these:

  host/usr/bin/go: No such file or directory

  http://autobuild.buildroot.net/results/6664189a6f3a815978e8d0a1d7ef408ca47e2874/

Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/go/go.mk

@@ -35,6 +35,14 @@ endif
 HOST_GO_DEPENDENCIES = host-go-bootstrap
 HOST_GO_ROOT = $(HOST_DIR)/usr/lib/go
 
+# The go build system doesn't have the notion of cross compiling, but just the
+# notion of architecture.  When the host and target architectures are different
+# it expects to be given a target cross compiler in CC_FOR_TARGET.  When the
+# architectures are the same it will use CC_FOR_TARGET for both host and target
+# compilation.  To work around this limitation build and install a set of
+# compiler and tool binaries built with CC_FOR_TARGET set to the host compiler.
+# Also, the go build system is not compatible with ccache, so use
+# HOSTCC_NOCCACHE.  See https://github.com/golang/go/issues/11685.
 HOST_GO_MAKE_ENV = \
 	GOROOT_BOOTSTRAP=$(HOST_GO_BOOTSTRAP_ROOT) \
 	GOROOT_FINAL=$(HOST_GO_ROOT) \
@@ -44,16 +52,29 @@ HOST_GO_MAKE_ENV = \
 	$(if $(GO_GOARM),GOARM=$(GO_GOARM)) \
 	GOOS=linux \
 	CGO_ENABLED=1 \
+	CC=$(HOSTCC_NOCCACHE)
+
+HOST_GO_TARGET_CC = \
 	CC_FOR_TARGET=$(TARGET_CC) \
 	CXX_FOR_TARGET=$(TARGET_CXX)
 
+HOST_GO_HOST_CC = \
+	CC_FOR_TARGET=$(HOSTCC_NOCCACHE) \
+	CXX_FOR_TARGET=$(HOSTCC_NOCCACHE)
+
+HOST_GO_TMP = $(@D)/host-go-tmp
+
 define HOST_GO_BUILD_CMDS
-	cd $(@D)/src && $(HOST_GO_MAKE_ENV) ./make.bash
+	cd $(@D)/src && $(HOST_GO_MAKE_ENV) $(HOST_GO_HOST_CC) ./make.bash
+	mkdir -p $(HOST_GO_TMP)
+	mv $(@D)/pkg/tool $(HOST_GO_TMP)/
+	mv $(@D)/bin/ $(HOST_GO_TMP)/
+	cd $(@D)/src && $(HOST_GO_MAKE_ENV) $(HOST_GO_TARGET_CC) ./make.bash
 endef
 
 define HOST_GO_INSTALL_CMDS
-	$(INSTALL) -D -m 0755 $(@D)/bin/go $(HOST_GO_ROOT)/bin/go
-	$(INSTALL) -D -m 0755 $(@D)/bin/gofmt $(HOST_GO_ROOT)/bin/gofmt
+	$(INSTALL) -D -m 0755 $(HOST_GO_TMP)/bin/go $(HOST_GO_ROOT)/bin/go
+	$(INSTALL) -D -m 0755 $(HOST_GO_TMP)/bin/gofmt $(HOST_GO_ROOT)/bin/gofmt
 
 	ln -sf ../lib/go/bin/go $(HOST_DIR)/usr/bin/
 	ln -sf ../lib/go/bin/gofmt $(HOST_DIR)/usr/bin/
@@ -62,7 +83,7 @@ define HOST_GO_INSTALL_CMDS
 
 	mkdir -p $(HOST_GO_ROOT)/pkg
 	cp -a $(@D)/pkg/include $(@D)/pkg/linux_* $(HOST_GO_ROOT)/pkg/
-	cp -a $(@D)/pkg/tool $(HOST_GO_ROOT)/pkg/
+	cp -a $(HOST_GO_TMP)/tool $(HOST_GO_ROOT)/pkg/
 
 	# There is a known issue which requires the go sources to be installed
 	# https://golang.org/issue/2775