build_helper: add gir build_helper

Manual.md

@@ -874,6 +874,9 @@ The current list of available `build_helper` scripts is the following:
 - `rust` specifies environment variables required for cross-compiling crates via cargo and
 for compiling cargo -sys crates.
 
+- `gir` specifies dependencies for native and cross builds to deal with
+GObject Introspection
+
 <a id="functions"></a>
 ### Functions
 

common/build-helper/gir.sh

@@ -0,0 +1,27 @@
+#
+# gir - build-helper for gobject-introspection
+#
+# This build-helper is used for packages that make use of
+# the GObject introspection middleware layer.
+# 
+
+# Check if the 'gir' build_option is set or if there is no
+# 'gir' build_option.
+if [ "$build_option_gir" ] || [[ $build_options != *"gir"* ]]; then
+	# Provide the host tooling, g-ir-scanner, g-ir-compiler and its
+	# wrappers.
+	hostmakedepends+=" gobject-introspection"
+	
+	if [ "$CROSS_BUILD" ]; then
+		# Required for running binaries produced from g-ir-compiler
+		# via g-ir-scanner-qemuwrapper
+		hostmakedepends+=" qemu-user-static"
+	
+		# Required for running the g-ir-scanner-lddwrapper
+		hostmakedepends+=" prelink-cross"
+
+		# Provide basic .gir types like GLib, GObject, DBus, Gio, cairo
+		# and tooling like g-ir-compiler
+		makedepends+=" gobject-introspection"
+	fi
+fi