Don't set cross-compilation variables in Makefile

This feature (cc_platform.mk and its sourcing from Makefiles) was added
by commit dac4171 ("runc-dmz: reduce memfd binary cloning cost
with small C binary") as part of dmz work.

From what I see, this is not needed for `make releaseall` as we already
set these variables using `set_cross_vars` shell function. My best guess
is this was mostly needed for testing (and for cross-i386 CI job).

The big issue though is these variables are guessed based on our
cross-compilation environment, meaning they won't work in other cases
(such as native compilation on non-x86_64 platforms, or using other
cross-compilation tools). One such example is Moby build which uses
https://github.com/tonistiigi/xx.

Besides, it's a duplication of effort in scripts/lib.sh, which is prone
to error.

Let's remove this from the Makefiles, and rework the script which sets
those variables so it can be used for other scenarios as well. For
example, to test cross-compilation locally (assuming we're in the same
environment as created by `make releaseall`), use

	$(./script/cross.sh $ARCH); make $TARGET

Signed-off-by: Kir Kolyshkin <[email protected]>

.github/workflows/test.yml

@@ -232,4 +232,4 @@ jobs:
     - name: unit test
       env:
         EXTRA_BUILDTAGS: ${{ matrix.dmz }}
-      run: sudo -E PATH="$PATH" -- make GOARCH=386 localunittest
+      run: sudo -E PATH="$PATH" sh -c "$(./script/cross.sh 386); make localunittest"

Dockerfile

@@ -56,7 +56,7 @@ RUN cd /tmp \
 
 # install libseccomp
 ARG LIBSECCOMP_VERSION
-COPY script/seccomp.sh script/lib.sh /tmp/script/
+COPY script/seccomp.sh script/cross.sh /tmp/script/
 RUN mkdir -p /opt/libseccomp \
     && /tmp/script/seccomp.sh "$LIBSECCOMP_VERSION" /opt/libseccomp 386 amd64 arm64 armel armhf ppc64le riscv64 s390x
 ENV LIBSECCOMP_VERSION=$LIBSECCOMP_VERSION

Makefile

@@ -3,9 +3,6 @@ SHELL = /bin/bash
 CONTAINER_ENGINE := docker
 GO ?= go
 
-# Get CC values for cross-compilation.
-include cc_platform.mk
-
 PREFIX ?= /usr/local
 BINDIR := $(PREFIX)/sbin
 MANDIR := $(PREFIX)/share/man

libcontainer/dmz/Makefile

@@ -1,5 +1,4 @@
-# Get GO, GOARCH and CC values for cross-compilation.
-include ../../cc_platform.mk
+STRIP ?= strip
 
 # List of GOARCH that nolibc supports, from:
 # 	https://go.dev/doc/install/source#environment (with GOOS=linux)

script/lib.sh → script/cross.sh

@@ -1,10 +1,8 @@
 #!/bin/bash
 
-# NOTE: Make sure you keep this file in sync with cc_platform.mk.
-
-# set_cross_vars sets a few environment variables used for cross-compiling,
+# Prints a few environment variables used for cross-compiling,
 # based on the architecture specified in $1.
-function set_cross_vars() {
+function print_cross_vars() {
 	GOARCH="$1" # default, may be overridden below
 	unset GOARM
 
@@ -79,5 +77,8 @@ function set_cross_vars() {
 	CC="${HOST:+$HOST-}gcc"
 	STRIP="${HOST:+$HOST-}strip"
 
-	export HOST CFLAGS GOARM GOARCH CC STRIP
+	[ -v GOARM ] && echo "export GOARM=$GOARM"
+	echo "export HOST=$HOST CFLAGS=\"$CFLAGS\" GOARCH=$GOARCH CC=$CC STRIP=$STRIP"
 }
+
+print_cross_vars "$1"

script/release_build.sh

@@ -22,9 +22,7 @@ set -e
 : "${LIBSECCOMP_VERSION:=2.5.5}"
 project="runc"
 root="$(readlink -f "$(dirname "${BASH_SOURCE[0]}")/..")"
-
-# shellcheck source=./script/lib.sh
-source "$root/script/lib.sh"
+cross="$root"/script/cross.sh
 
 # This function takes an output path as an argument, where the built
 # (preferably static) binary should be placed.
@@ -68,7 +66,8 @@ function build_project() {
 	for arch in "${arches[@]}"; do
 		# Reset CFLAGS.
 		CFLAGS="$original_cflags"
-		set_cross_vars "$arch"
+		# Obtain cross-compilation environment variables.
+		eval "$($cross "$arch")"
 		make -C "$root" \
 			PKG_CONFIG_PATH="$seccompdir/$arch/lib/pkgconfig" \
 			"${make_args[@]}"

script/seccomp.sh

@@ -1,9 +1,7 @@
 #!/bin/bash
 
 set -e -u -o pipefail
-
-# shellcheck source=./script/lib.sh
-source "$(dirname "${BASH_SOURCE[0]}")/lib.sh"
+cross="$(dirname "${BASH_SOURCE[0]}")/cross.sh"
 
 # sha256 checksums for seccomp release tarballs.
 declare -A SECCOMP_SHA256=(
@@ -48,7 +46,8 @@ function build_libseccomp() {
 	for arch in "${arches[@]}"; do
 		# Reset CFLAGS.
 		CFLAGS="$original_cflags"
-		set_cross_vars "$arch"
+		# Obtain cross-compilation environment variables.
+		eval "$($cross "$arch")"
 		./configure --host "$HOST" \
 			--prefix="$dest/$arch" --libdir="$dest/$arch/lib" \
 			--enable-static --enable-shared