[gcc r13-8029] libstdc++: Fix testsuite no_pch directive

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:5d036ff51e2491401b9a64705bfd7f7467764260

commit r13-8029-g5d036ff51e2491401b9a64705bfd7f7467764260
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Aug 16 21:46:05 2023 +0100

    libstdc++: Fix testsuite no_pch directive
    
    The { dg-add-options no_pch } directive is supposed to add a macro
    definition that invalidates the PCH file, and ensures that the #include
    directives in the test file are processed as written. But the proc that
    adds the options actually removes all existing options, cancelling out
    any previous dg-options directive.
    
    This means that using no_pch will cause FAILs in a file that relies on
    other options set by an earlier dg-options.
    
    The no_pch directive was added for PR libstdc++/21769 where Janis
    suggested adding it as return "$flags -D__GLIBCXX__=99999999" but what
    was actually committed didn't include the $flags so replaced them.
    
    Additionally, using no_pch  only prevents the precompiled version of
    <bits/stdc++.h> from being included, it doesn't prevent the
    non-precompiled version being included by -include bits/stdc++.h in the
    test flags. Use regsub to filter that out of the options as well.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/lib/dg-options.exp (add_options_for_no_pch): Remove
            any "-include bits/stdc++.h" from options and add the macro to
            the existing options instead of replacing them.
    
    (cherry picked from commit 91315f23ba127ea4d1a584023bae34e143f6eb8c)

Diff:
---
 libstdc++-v3/testsuite/lib/dg-options.exp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/lib/dg-options.exp b/libstdc++-v3/testsuite/lib/dg-options.exp
index 73c1552e682..15e34f8a646 100644
--- a/libstdc++-v3/testsuite/lib/dg-options.exp
+++ b/libstdc++-v3/testsuite/lib/dg-options.exp
@@ -269,8 +269,10 @@ proc dg-require-target-fs-lwt { args } {
 }
 
 proc add_options_for_no_pch { flags } {
+    # Remove any inclusion of bits/stdc++.h from the options.
+    regsub -all -- "-include bits/stdc...h" $flags "" flags
     # This forces any generated and possibly included PCH to be invalid.
-    return "-D__GLIBCXX__=99999999"
+    return "$flags -D__GLIBCXX__=99999999"
 }
 
 # Add to FLAGS all the target-specific flags needed for networking.