Add more files to the musl sysroot for rustc builds

Add libc++.a and the clang crtbegin and crtend objects to the musl
sysroot to allow building rustc against it.  The crtbegin and crtend
objects are also copied to all the different names gcc uses, as
clang uses the same object for all build types.

Bug: 216192129
Test: rustc builds
Change-Id: I681f90ee381405be50f32763d85e1f486fff142a
1 file changed