PKGBUILD.5: Fix typo

Signed-off-by: André Schröder <andre.schroedr@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>

doc/PKGBUILD.5.asciidoc

@@ -361,7 +361,7 @@ function.
 	is skipped.
 
 *build() Function*::
-	The optional `build()` function is use to compile and/or adjust the source
+	The optional `build()` function is used to compile and/or adjust the source
 	files in preparation to be installed by the `package()` function.
 
 *check() Function*::