Why build sysroot from source code about gcc-toolchain

[Riatre]

First, this is more like a discussion instead of an issue.

From README.md:

When it comes to building portable ELF binaries, the libc plays an important role. The linker will try to link against new symbols, and since the GNU libc has symbol versioning, linking against a newer glibc will prevent that program from running on a system using an older glibc. To solve this, we ship glibc 2.26 with the sysroots, which should be old enough by now to make all programs compiled with this toolchain portable.

We need a specific version of glibc in the sysroot, which may or may not match the one shipped by your (or any) distro.

[f0rmiga]

Thanks @Riatre for the answer. To add one more bit that's not in the README, I found that libgfortran.a from the Ubuntu distro (IIRC) is unusable. Even though it's provided, I remember facing issues during linking.

Having everything built from source gives more freedom to overcome this kind of issue more quickly. I'm always happy to discuss any concerns people may have when building from source, but so far, I only got good feedback from it.

@SWYZZWH Anything specific that comes to your mind that's concerning?