Smarter auto unlock build supporting CTRL-C

Catch all exists equally, success or any error case
including CTRL-C to unlock the build.

This way we do not have to manually catch all exits.
The lock should never get stuck because we do never build
twice in a row from one script.

Even ./loop_gdb.sh launches ./update.sh and as soon as it
is finished the build lock is freed.

If for whatever reason we need to build multiple times in
a row the manual `unlock_build` calls have
to be reintroduced.

Author: ChillerDragon

lib/include/build_lock.sh

@@ -130,6 +130,7 @@ function lock_build() {
 	# lock the build
 	printf '%s %s %s %s\n' "$CFG_GIT_PATH_MOD" "$SERVER_UUID" "$$" "$(date '+%s')" >> "$BUILD_LOCKFILE"
 	_meta_unlock || return 1
+	trap unlock_build EXIT
 }
 
 function unlock_build() {

lib/include/update/cmake.sh

@@ -161,7 +161,6 @@ function cmake_update() {
 		err       "       cd $arg_git_path"
 		err       "       git status"
 		err       "       $(tput bold)./update.sh --force$(tput sgr0) to ignore"
-		unlock_build
 		exit 1
 	fi
 	current_branch="$(git rev-parse --abbrev-ref HEAD)"
@@ -230,7 +229,6 @@ function cmake_update() {
 	if [ "$build_fail" == "1" ]
 	then
 		err --log "build failed."
-		unlock_build
 		exit 1
 	fi
 	if [ ! -f "$arg_compiled_bin" ]

update.sh

@@ -225,15 +225,12 @@ then
 	then
 		custom_update_teeworlds "$@"
 	else
-		unlock_build
 		err "Unsupported build system: $CFG_BUILD_SYSTEM"
 		exit 1
 	fi
 	map_themes_post
 	git_save_pull
 	update_lua
-
-	unlock_build
 elif [ "$CFG_SERVER_TYPE" == "tem" ] || [ "$arg_type" == "tem" ]
 then
 	if [ "$arg_refresh" == "1" ]