[PATCH] configure: fix backwards-compatibility for meson sphinx_build option

[Paolo Bonzini]

Reintroduce the cmd_line.txt mangling to remove the sphinx_build
option when rerunning meson.  The mechanism was removed in
commit 75cc28648574 ("configure: remove backwards-compatibility code", 
2023-01-11)
because it was obsolete at the time, but the Meson deprecation
mechanism doesn't quite work when options are finally removed.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 configure | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/configure b/configure
index 43620b80c8df..b61475a4cb5d 100755
--- a/configure
+++ b/configure
@@ -1984,6 +1984,14 @@ if test "$skip_meson" = no; then
   if test "$?" -ne 0 ; then
       error_exit "meson setup failed"
   fi
+else
+  if test -f meson-private/cmd_line.txt; then
+    # Adjust old command line options that were removed
+    # sed -i is not portable
+    perl -i -ne '
+      /^sphinx_build/ && next;
+      print;' meson-private/cmd_line.txt
+  fi
 fi
 
 # Save the configure command line for later reuse.
-- 
2.40.1