Fix for support on Alpine and others musl-based distros

[igk1972]

Alpine Linux doesn't support GLOB_BRACE since it is using musl libc instead of GNU libc.

I was trying to compile static assets on an Alpine Linux Docker container (popular case). I was unable to, because there is a error around usage of the GLOB_BRACE constant, which may or may not be defined depending on the environment, and isn't defined/worked in Alpine Linux.

Using an Alpine Linux PHP Docker container, for running Phulp:
PHP 7.1 (Alpine Linux 3.7)

The following:

[Exception]
Notice: Use of undefined constant GLOB_BRACE - assumed 'GLOB_BRACE' in /app/php_packages/reisraff/phulp/bin/phulp.php on line 145

[reisraff]

Oh, man, I appreciate your contribution, but since, we had the problem of autoload, we must take on mind that until this line https://github.com/igk1972/phulp/blob/64dd84392b24b5bb873708a0c2268e16f0af4a26/bin/phulp.php#L64 we dont have sure that the autoload was successfuly initialized.

So I liked you PR, I just would ask you to change this behavior for, ask the files with glob, and assert the name with regex, that ensure we are not using dependencies on the phulp.php (bootstraper).

Thanks man.