The last change to src/core/main.c from 24th January  makes mutter unbuildable in jhbuild
The error is:
  CC     main.o
cc1: warnings being treated as errors
core/main.c: In function ‘sigterm_handler’:
core/main.c:445: error: ignoring return value of ‘write’, declared with attribute warn_unused_result
make[4]: *** [main.o] Error 1

With the old code I am able to build.

The changes are:
git diff 48b9807c86d520b4b007dd0a438f3c5d72a9a477..4f079affea4a9d55a97c7150c2973c69166bc64e src/core/main.c
diff --git a/src/core/main.c b/src/core/main.c
index 9efb549..1ea6f5d 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -442,9 +442,7 @@ sigterm_handler (int signum)
 {
   if (sigterm_pipe_fds[1] >= 0)
     {
-      int dummy;
-
-      dummy = write (sigterm_pipe_fds[1], "", 1);
+      (void) write (sigterm_pipe_fds[1], "", 1);
       close (sigterm_pipe_fds[1]);
       sigterm_pipe_fds[1] = -1;
     }