Regressions on releases/gcc-10 at commit r10-9459 vs commit r10-9450 on Linux/x86_64

[H.J. Lu]

New failures:

New passes:
FAIL: gcc.dg/attr-flatten-1.c  (test for warnings, line 13)
FAIL: gcc.dg/attr-flatten-1.c  (test for warnings, line 13)
FAIL: gcc.dg/attr-flatten-1.c  (test for warnings, line 13)