Remove gcc tools from script.

Replace all references to gcc tools with llvm tools. This change still
uses c++filt until llvm-cxxfilt is put in the prebuilts.

Test: Ran a backtrace through this script and the old script and verified
Test: no major differences.
Test: Ran unittests for symbol.py and stack_core.py.
Change-Id: Ic31c1a0707dae11c5037f9637943cd7932badf46
2 files changed