Automatically update pkgver using makepkg

[j-waters]

If a pkgver() function exists, the PKGBUILD file will be copied into a new temporary directory, makepkg -od will be run, and then the new PKGBUILD file will be the one that is copied into the aur repo.

makepkg -od:

• -o skips building, but still runs pkgver()
• -d skips dependency checks, which is fine as long as no dependencies (other than git) are used in the pkgver() function

[KSXGitHub]

It seems that you're busy. Notify me by @ mention when you're done.

[yuezk]

Hi @KSXGitHub Is it ready to merge this PR?

[yuezk]

@KSXGitHub I submitted another PR (#26) for updating the pkgver, it will work with the case where the PKGBUILD depends on the local source code tarballs in the package repository. Please also take a look. Thanks.