test-kernel-install: support the case when custom default locale is specified

This also makes 'diff' command output to stderr, otherwise the
difference is eaten by meson by default, so hard to debug.

src/kernel-install/test-kernel-install.sh

@@ -291,7 +291,7 @@ rmdir "$BOOT_ROOT/hoge"
 ###########################################
 output="$("$kernel_install" -v --json=pretty inspect 1.1.1 "$D/sources/linux")"
 
-diff -u <(echo "$output") - <<EOF
+diff -u <(echo "$output") - >&2 <<EOF
 {
 	"MachineID" : "3e0484f3634a418b8e6a39e8828b03e3",
 	"KernelImageType" : "unknown",
@@ -309,7 +309,7 @@ diff -u <(echo "$output") - <<EOF
 		"$D/00-skip.install"
 	],
 	"PluginEnvironment" : [
-		"LC_COLLATE=C.UTF-8",
+		"LC_COLLATE=$SYSTEMD_DEFAULT_LOCALE",
 		"KERNEL_INSTALL_VERBOSE=1",
 		"KERNEL_INSTALL_IMAGE_TYPE=unknown",
 		"KERNEL_INSTALL_MACHINE_ID=3e0484f3634a418b8e6a39e8828b03e3",

src/test/meson.build

@@ -14,6 +14,7 @@ path = run_command(sh, '-c', 'echo "$PATH"', check: true).stdout().strip()
 test_env = {
         'PATH' : meson.project_build_root() + ':' + path,
         'PROJECT_BUILD_ROOT' : meson.project_build_root(),
+        'SYSTEMD_DEFAULT_LOCALE' : get_option('default-locale'),
         'SYSTEMD_SLOW_TESTS' : want_slow_tests ? '1' : '0',
         'PYTHONDONTWRITEBYTECODE' : '1',
 }