Use sysroot and native-system-header-dir

[fjtrujy]

Description

I was trying to compile https://github.com/google/googletest for PSP and I was facing some errors when finding the MAX_PATH macro.

Then I faced that the generated header files for GCC step 2 they weren't generated properly.
Afther some days of investigation I have been able to find out where the issue was, we missed the usage of sysroot and native-system-header-dir

I have made also some clean up in the scripts:

• Remove all the exit 1 as we have defined the onerr function.
• Reduce GCC phase 1 compilation
• Other minor changes.

Once merged I will add googletest as dependency in psp-packages in this way we could at least notice in the future similar issues.

This PR deprecates the previous one #36.

Cheers.

[fjtrujy]

@davidgfnet please double-check that everything is working as expected.
And feel free to add more info if you think it is relevant.

Cheers.

[davidgfnet]

Works as expected for me!