makepkg: fix broken check for the fakeroot binary

In commit d8ee8d0c99 we made use of
fakeroot absolutely mandatory, and disabled a lot of the code which
checked to see if this now-defunct BUILDENV option was set, before
setting up the environment to use fakeroot. Unfortunately, we missed one
spot.

The check_software routine still checked to see if fakeroot was
enabled, but due to the option being removed, thought that it was in
fact disabled, and as a result this check would never run.

Fix by checking to see if we are trying to build either a package or a
source package, and if so, checking for fakeroot. These are the only two
situations where fakeroot is needed.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/libmakepkg/executable/fakeroot.sh.in

@@ -28,7 +28,7 @@ source "$LIBRARY/util/option.sh"
 executable_functions+=('executable_fakeroot')
 
 executable_fakeroot() {
-	if check_buildenv "fakeroot" "y" && (( EUID > 0 )); then
+	if (( SOURCEONLY || BUILDPKG )); then
 		if ! type -p fakeroot >/dev/null; then
 			error "$(gettext "Cannot find the %s binary.")" "fakeroot"
 			return 1