Revert "BUILD: Merge libm to libc"

 - We have all-in-one mode in near future!

This reverts commit fc8e92e861b0ec0fd705979fcab6f23a88f8f4fe
BUILD: Add all-in-one mode

 - libc, libdl,libm and dynamic linker all integrated into olibc.so in all-in-one mode.
 - Filter out libc, libdl and libm in all-in-one-mode.
 - Make a special case for olibc.so in normalize-libraries since it's
   not prefix with `lib`.