llvm: update to 3.8.0.

Use cmake to build.  This is the favored method of building by upstream.

Consequences:
- Build lld again
- Build LLVMgold
- Enable sanitizers on non-musl platforms
- Remove llvm-doc (not built by cmake, quite useless)
- Use versioned binary names
- Could use ninja with make_cmd=ninja and configure -Gninja, but we
  stick to make for now.

Also cleaned up and fixed remaining patches.

common/shlibs

@@ -948,6 +948,7 @@ libLLVM-3.5.so libllvm-3.5.0_1
 libLLVM-3.6.so libllvm3.6-3.6.0_1
 libLLVM-3.7.so libllvm3.7-3.7.0_1
 libLLVM-3.7.1.so libllvm3.7-3.7.1_1
+libLLVM-3.8.so libllvm3.8-3.8.0_1
 libisofs.so.6 libisofs-0.6.24_1
 libbfd-2.22.so binutils-2.22_1<2.23_1
 libopcodes-2.22.so binutils-2.22_1<2.23_1