Ensure pkgbase/epoch are defined before doing anything

When generating integrity sums, we could get some weird output before due to
epoch being uninitialized:

    /usr/bin/makepkg: line 234: [[: 2.6.37: syntax error: invalid arithmetic operator (error token is ".6.37")

Signed-off-by: Dan McGee <dan@archlinux.org>

scripts/makepkg.sh.in

@@ -1850,6 +1850,10 @@ else
 	source "$BUILDFILE"
 fi
 
+# set defaults if they weren't specified in buildfile
+pkgbase=${pkgbase:-${pkgname[0]}}
+epoch=${epoch:-0}
+
 if (( GENINTEG )); then
 	mkdir -p "$srcdir"
 	chmod a-s "$srcdir"
@@ -1859,9 +1863,6 @@ if (( GENINTEG )); then
 	exit 0 # $E_OK
 fi
 
-pkgbase=${pkgbase:-${pkgname[0]}}
-epoch=${epoch:-0}
-
 # check the PKGBUILD for some basic requirements
 check_sanity || exit 1