[Chapel Merge] Fix a % format mismatch that clang 10 was complain

Branch: refs/heads/master
Revision: 8fe1586
Author: bradcray
Log Message:

Merge pull request #17869 from bradcray/fix-ofi-printf-for-llvm10

Fix a % format mismatch that clang 10 was complaining about for comm=ofi

[reviewed by @gbtitus]

Trying CHPL_COMM=ofi on my Mac with CHPL_DEVELOPER set, I was getting
a broken build due to a %-format mismatch. This resolves it by using the stdint.h
macros for fixed-size int formats.

Modified Files:
M runtime/src/comm/ofi/comm-ofi.c

Compare: https://github.com/chapel-lang/chapel/compare/9702cc9e3ba0...8fe1586c3bb6