Regressions on master at commit r15-6119 vs commit r15-6115 on Linux/x86_64

[Haochen Jiang]

Regressions on master at commit r15-6119 vs commit r15-6115 on Linux/x86_64
New failures:
FAIL: 30_threads/async/async.cc  -std=gnu++17 execution test

New passes:
FAIL: gcc.dg/torture/convert-dfp-2.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
FAIL: gcc.dg/torture/convert-dfp.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)