Remove unsupported targets

src/unix/uclibc/mod.rs

src/unix/uclibc/other/b32/arm.rs

src/unix/uclibc/other/b32/mod.rs

src/unix/uclibc/other/b32/powerpc.rs

src/unix/uclibc/other/b32/x86.rs

src/unix/uclibc/other/b64/aarch64.rs

src/unix/uclibc/other/b64/mod.rs

src/unix/uclibc/other/b64/powerpc64.rs

src/unix/uclibc/other/b64/sparc64.rs

src/unix/uclibc/other/b64/x86_64.rs

src/unix/uclibc/other/mod.rs

src/unix/uclibc/s390x.rs