gdk: Emit stamp-gc-h in the correct directory
Update git.mk

This fixes the .deps of subdirs (a11y, deprecated, inspector) not
showing up in .gitignore.
actions: Fix compile warning
Whitespace fixes
stylecontext: Make sure we always clear the cache when the CSS changes

After b49c7c34214da2d8d5e6dae2e8d0b0fe1b23f68e we were no longer doing a
full revalidate after GTK_CSS_CHANGE_SOURCE changes.

This fixes spurious failures of widgets not properly updating when
changing the theme.