Merge branch 'prog-cc-c-o-work' into maint

* prog-cc-c-o-work:
  tests: some tests make no sense if "$CC -c -o" doesn't work
  AM_PROG_CC_C_O: don't rely on AC_PROG_CC_C_O, re-implement similar logic
  compile: rewrite AC_PROG_CC with AM_PROG_CC_C_O contents

diff --cc NEWS
Simple merge

diff --cc m4/prog-cc-c-o.m4
Simple merge

diff --cc t/ax/am-test-lib.sh
Simple merge