[glibc] build-many-glibcs.py: Do not build C++ PCHs by default

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3aec0c3912859bcf0432c700a8fbdcb23b45545f

commit 3aec0c3912859bcf0432c700a8fbdcb23b45545f
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Dec 17 16:23:08 2019 +0100

    build-many-glibcs.py: Do not build C++ PCHs by default
    
    They are not used during the subsequent glibc build, so creating them
    merely wastes time.

Diff:
---
 scripts/build-many-glibcs.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/scripts/build-many-glibcs.py b/scripts/build-many-glibcs.py
index 193d497..92cc613 100755
--- a/scripts/build-many-glibcs.py
+++ b/scripts/build-many-glibcs.py
@@ -1382,9 +1382,12 @@ class Config(object):
         else:
             tool_build = 'gcc'
             # libsanitizer commonly breaks because of glibc header
-            # changes, or on unusual targets.
+            # changes, or on unusual targets.  C++ pre-compiled
+            # headers are not used during the glibc build and are
+            # expensive to create.
             if not self.ctx.full_gcc:
-                cfg_opts += ['--disable-libsanitizer']
+                cfg_opts += ['--disable-libsanitizer',
+                             '--disable-libstdcxx-pch']
             langs = 'all' if self.ctx.full_gcc else 'c,c++'
             cfg_opts += ['--enable-languages=%s' % langs,
                          '--enable-shared', '--enable-threads']