Check for invalid symbol names in llvm-nm output.

See #12551
and:
#17826

Older versions of llvm didn't used to mangle these __invoke symbols.

Author: sbc100

tools/building.py

@@ -575,6 +575,9 @@ def parse_llvm_nm_symbols(output):
       filename_pos = entry_pos
 
     filename = line[:filename_pos]
+    if entry_pos + 14 >= len(line):
+      exit_with_error('error parsing output of llvm-nm: `%s`\nIf the symbol name here contains a colon, and starts with __invoke_, then the object file was likely built with and old version of llvm.' % line)
+
     status = line[entry_pos + 11] # Skip address, which is always fixed-length 8 chars.
     symbol = line[entry_pos + 13:]