[1.11>master] [MERGE #6331 @boingoing] Fix build errors related to literals in assembly while using Clang 8.0.

Merge pull request #6331 from boingoing:port_clang_fix_release_1_11

Cherry-pick of 20b819a5a7ff09577a61582059259f67729cde0c and 479c3bd77 from master to fix building release/1.11 on newer versions of Clang. This will fix the MacOS CI build on github.