busybox: always start do_compile with orig config files

When compiling busybox a second time (e.g. with `compile -f`), busybox
can use an altered autoconf.h file for compiling, which can ultimately
produces different and unwanted binaries.

This can produce errors like this one:

ERROR: busybox-1.35.0-r0 do_package: Error executing a python function in exec_func_python() autogenerated:
The stack trace of python calls that resulted in this exception/failure was:
File: 'exec_func_python() autogenerated', lineno: 2, function: <module>
     0001:
 *** 0002:ptest_update_alternatives(d)
     0003:
File: '…/poky/meta/classes/ptest.bbclass', lineno: 100, function: ptest_update_alternatives
     0096:        for alt_name, alt_link, alt_target, _ in alternatives:
     0097:            # Some alternatives are for man pages,
     0098:            # check if the alternative is in PATH
     0099:            if os.path.dirname(alt_link) in bin_paths:
 *** 0100:                os.symlink(alt_target, os.path.join(ptest_bindir, alt_name))
     0101:}
     0102:
     0103:do_configure_ptest_base[dirs] = "${B}"
     0104:do_compile_ptest_base[dirs] = "${B}"
Exception: FileExistsError: [Errno 17] File exists: '/bin/busybox.suid' -> '…/busybox/1.35.0-r0/package/usr/lib/busybox/ptest/bin/login'

This happens because ALTERNATIVE:busybox contains `/bin/login` twice,
initially that's because `/bin/login` is present in both
busybox.links.suid and busybox.links.nosuid. The reason for that is
because of the altered autoconf.h.

Steps to reproduce above error:

<add ptest to distro configs>
bitbake busybox -c clean
bitbake busybox -c package -f
bitbake busybox -c compile -f
bitbake busybox -c package -f

This patch guards against potential bugs by:

- making a backup of .config and autoconf.h that have matching
  timestamps.
- make sure do_compile always starts with these files.
- restore .config and autoconf.h at the end of do_compile.

(From OE-Core rev: 7ef76eaf5b68d52afdc4292bbe20309e29bb464a)

Signed-off-by: Antonin Godard <antoningodard@pm.me>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/busybox/busybox.inc

@@ -139,6 +139,10 @@ do_configure () {
 	do_prepare_config
 	merge_config.sh -m .config ${@" ".join(find_cfgs(d))}
 	cml1_do_configure
+
+	# Save a copy of .config and autoconf.h.
+	cp .config .config.orig
+	cp include/autoconf.h include/autoconf.h.orig
 }
 
 do_compile() {
@@ -146,13 +150,14 @@ do_compile() {
 	if [ "${BUILD_REPRODUCIBLE_BINARIES}" = "1" ]; then
 		export KCONFIG_NOTIMESTAMP=1
 	fi
+
+	# Ensure we start do_compile with the original .config and autoconf.h.
+	# These files should always have matching timestamps.
+	cp .config.orig .config
+	cp include/autoconf.h.orig include/autoconf.h
+
 	if [ "${BUSYBOX_SPLIT_SUID}" = "1" -a x`grep "CONFIG_FEATURE_INDIVIDUAL=y" .config` = x ]; then
 		# split the .config into two parts, and make two busybox binaries
-		if [ -e .config.orig ]; then
-			# Need to guard again an interrupted do_compile - restore any backup
-			cp .config.orig .config
-		fi
-		cp .config .config.orig
 		oe_runmake busybox.cfg.suid
 		oe_runmake busybox.cfg.nosuid
 
@@ -189,15 +194,18 @@ do_compile() {
 			bbfatal "busybox suid binary incorrectly provides /bin/sh"
 		fi
 
-		# copy .config.orig back to .config, because the install process may check this file
-		cp .config.orig .config
 		# cleanup
-		rm .config.orig .config.app.suid .config.app.nosuid .config.disable.apps .config.nonapps
+		rm .config.app.suid .config.app.nosuid .config.disable.apps .config.nonapps
 	else
 		oe_runmake busybox_unstripped
 		cp busybox_unstripped busybox
 		oe_runmake busybox.links
 	fi
+
+	# restore original .config and autoconf.h, because the install process
+	# may check these files
+	cp .config.orig .config
+	cp include/autoconf.h.orig include/autoconf.h
 }
 
 do_install () {