unix/main: Fix GCC builds for RISC-V 64 bits.

This contains a workaround to silence a possibly incorrect warning when
building the Unix port with GCC targeting RISC-V 64 bits.

Fixes issue micropython#12838.

Signed-off-by: Alessandro Gatti <[email protected]>

Author: agatti

ports/unix/main.c

@@ -562,7 +562,12 @@ MP_NOINLINE int main_(int argc, char **argv) {
             // First entry is empty. We've already added an empty entry to sys.path, so skip it.
             ++path;
         }
-        bool path_remaining = *path;
+        // GCC targeting RISC-V 64 reports a warning about `path_remaining` being clobbered by
+        // either setjmp or vfork if that variable it is allocated on the stack.  This may
+        // probably be a compiler error as it occurs on a few recent GCC releases (up to 14.1.0)
+        // but LLVM doesn't report any warnings.
+        static bool path_remaining;
+        path_remaining = *path;
         while (path_remaining) {
             char *path_entry_end = strchr(path, PATHLIST_SEP_CHAR);
             if (path_entry_end == NULL) {