PKGBUILD: Optionally build with colord

Closes #73.

'colord' may be necessary for colour profile support, but it can be
built without if the user doesn't have this package installed.

.github/workflows/main.yml

@@ -58,7 +58,7 @@ jobs:
         CFLAGS+=" -DG_ENABLE_DEBUG -DG_DISABLE_CAST_CHECKS"
         meson gtk+-${_gtkver} build \
             -D broadway_backend=true \
-            -D colord=no \
+            -D colord=auto \
             -D demos=true \
             -D examples=false \
             -D tests=false \

PKGBUILD

@@ -119,7 +119,7 @@ build()
 	# 64-bit
 	arch-meson gtk+-$_gtkver build \
 		-D broadway_backend=true \
-		-D colord=no \
+		-D colord=auto \
 		-D demos=true \
 		-D examples=false \
 		-D tests=false \
@@ -136,7 +136,7 @@ build()
 
 	linux32 arch-meson gtk+-$_gtkver build32 \
 		-D broadway_backend=true \
-		-D colord=no \
+		-D colord=auto \
 		-D demos=false \
 		-D examples=false \
 		-D introspection=false \