package/pkg-golang: support _SUBDIR

Some packages have their actual source tree in a sub-directory (even if
that is the only source in the repository); this is the case for example
with the Amazon ECR credential helper (to be packaged in a follow up
commit):
    https://github.com/awslabs/amazon-ecr-credential-helper

Do the build in _SUBDIR, and also do the vendoring in there.

We don't need the build to generate executables inside _SUBDIR, so we
just keep using $(@D)/bin as a place to generate them (and install them
from).

Signed-off-by: Yann E. MORIN <yann.morin@orange.com>
Cc: Christian Stewart <christian@aperture.us>
Reviewed-by: Christian Stewart <christian@aperture.us>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/pkg-golang.mk

@@ -79,8 +79,8 @@ $(2)_GOMOD ?= $$($(2)_SRC_DOMAIN)/$$($(2)_SRC_VENDOR)/$$($(2)_SRC_SOFTWARE)
 # Generate a go.mod file if it doesn't exist. Note: Go is configured
 # to use the "vendor" dir and not make network calls.
 define $(2)_GEN_GOMOD
-	if [ ! -f $$(@D)/go.mod ]; then \
-		printf "module $$($(2)_GOMOD)\n" > $$(@D)/go.mod; \
+	if [ ! -f $$(@D)/$$($(2)_SUBDIR)/go.mod ]; then \
+		printf "module $$($(2)_GOMOD)\n" > $$(@D)/$$($(2)_SUBDIR)/go.mod; \
 	fi
 endef
 $(2)_POST_PATCH_HOOKS += $(2)_GEN_GOMOD
@@ -91,6 +91,11 @@ $(2)_DL_ENV += \
 	GOPROXY=direct \
 	$$($(2)_GO_ENV)
 
+# If building in a sub directory, do the vendoring in there
+ifneq ($$($(2)_SUBDIR),)
+$(2)_DOWNLOAD_POST_PROCESS_OPTS += -s$$($(2)_SUBDIR)
+endif
+
 # Because we append vendored info, we can't rely on the values being empty
 # once we eventually get into the generic-package infra. So, we duplicate
 # the heuristics here
@@ -135,7 +140,7 @@ endif
 # Build package for target
 define $(2)_BUILD_CMDS
 	$$(foreach d,$$($(2)_BUILD_TARGETS),\
-		cd $$(@D); \
+		cd $$(@D)/$$($(2)_SUBDIR); \
 		$$(HOST_GO_TARGET_ENV) \
 			$$($(2)_GO_ENV) \
 			$$(GO_BIN) build -v $$($(2)_BUILD_OPTS) \
@@ -147,7 +152,7 @@ else
 # Build package for host
 define $(2)_BUILD_CMDS
 	$$(foreach d,$$($(2)_BUILD_TARGETS),\
-		cd $$(@D); \
+		cd $$(@D)/$$($(2)_SUBDIR); \
 		$$(HOST_GO_HOST_ENV) \
 			$$($(2)_GO_ENV) \
 			$$(GO_BIN) build -v $$($(2)_BUILD_OPTS) \

support/download/go-post-process

@@ -5,10 +5,11 @@ set -e
 . "${0%/*}/helpers"
 
 # Parse our options
-while getopts "n:o:" OPT; do
+while getopts "n:o:s:" OPT; do
     case "${OPT}" in
     o)  output="${OPTARG}";;
     n)  base_name="${OPTARG}";;
+    s)  subdir="${OPTARG}";;
     :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
     \?) error "unknown option '%s'\n" "${OPTARG}";;
     esac
@@ -22,7 +23,7 @@ fi
 post_process_unpack "${base_name}" "${output}"
 
 # Do the Go vendoring
-pushd "${base_name}" > /dev/null
+pushd "${base_name}/${subdir}" > /dev/null
 
 if [ ! -f go.mod ]; then
     echo "ERROR: no vendor/ folder and no go.mod, aborting"