You're not understanding. The first example "requires glibc" because the binaries were linked against glibc, just like they'd be linked against OS X's libc if they'd been built for OS X.
The second example is, again, an issue of gcc being built against glibc. You can build it against any libc you want, but when built against glibc, the resulting binaries are obviously going to use glibc.
You appear to have a fundamental misunderstanding of the difference between the requirements of source code, and the requirements of the binaries built from them. The latter are not the same as the former, and will vary depending on how you built the source code.
And when I just built gfortran, it didn't complain about the lack of glibc at all. If yours was complaining, I think you must have configured something incorrectly, though it escapes me what that could be.
The second example is, again, an issue of gcc being built against glibc. You can build it against any libc you want, but when built against glibc, the resulting binaries are obviously going to use glibc.
You appear to have a fundamental misunderstanding of the difference between the requirements of source code, and the requirements of the binaries built from them. The latter are not the same as the former, and will vary depending on how you built the source code.
And when I just built gfortran, it didn't complain about the lack of glibc at all. If yours was complaining, I think you must have configured something incorrectly, though it escapes me what that could be.