Sandbox libc_musl_sysroot_bits

Sandboxing it produces this diff:

  $ diff <(zipinfo -l out_not_sandboxed/soong/.intermediates/external/musl/libc_musl_sysroot_bits/linux_glibc_x86_64/gen/  libc_musl_sysroot_bits.zip) <(zipinfo -l out/soong/.intermediates/external/musl/libc_musl_sysroot_bits/linux_glibc_x86_64/gen/  libc_musl_sysroot_bits.zip)
  1,3c1,2
  < Archive:  out_not_sandboxed/soong/.intermediates/external/musl/libc_musl_sysroot_bits/linux_glibc_x86_64/gen/  libc_musl_sysroot_bits.zip
  < Zip file size: 8535 bytes, number of entries: 16
  < -rw-r--r--  2.0 unx      421 bl      225 defN 08-Jan-01 00:00 include/bits/alltypes.h.in
  ---
  > Archive:  out/soong/.intermediates/external/musl/libc_musl_sysroot_bits/linux_glibc_x86_64/gen/libc_musl_sysroot_bits.zip
  > Zip file size: 5358 bytes, number of entries: 14
  17d15
  < -rw-r--r--  2.0 unx    10384 bl     2666 defN 08-Jan-01 00:00 include/bits/syscall.h.in
  19c17
  < 16 files, 21039 bytes uncompressed, 6439 bytes compressed:  69.4%
  ---

So the alltypes.h.in and syscall.h.in are removed from the zip after
sandboxing. This seems good, because those two files are handled
separately already in that Android.bp file, and are not regular header
files like the rest of the zip file.

Bug: 307824623
Test: ./build/soong/tests/genrule_sandbox_test.py libc_musl_sysroot_bits
Change-Id: I46b6340046ad7df85ea4fc9c54b46ade305661e6