Regressions on master at commit r15-2172 vs commit r15-2165 on Linux/x86_64

[Haochen Jiang]

Regressions on master at commit r15-2172 vs commit r15-2165 on Linux/x86_64
New failures:
FAIL: c-c++-common/musttail12.c  -std=c++14 (test for excess errors)
FAIL: c-c++-common/musttail12.c  -std=c++17 (test for excess errors)
FAIL: c-c++-common/musttail12.c  -std=c++20 (test for excess errors)
FAIL: g++.dg/musttail6.C   (test for excess errors)

New passes: