Bug 1847101 - Define WORDS_BIGENDIAN when targeting big endians. r=firefox-build-system-reviewers,ahochheiden

Some third party code (cairo, pixman, some media libs) rely on this
define being set. When they are built standalone, they get it from
autoconf, but we don't run their configure scripts, so that's missed.

Differential Revision: https://phabricator.services.mozilla.com/D185351

build/moz.configure/init.configure

@@ -776,6 +776,11 @@ set_config("HAVE_64BIT_BUILD", have_64_bit)
 set_define("HAVE_64BIT_BUILD", have_64_bit)
 add_old_configure_assignment("HAVE_64BIT_BUILD", have_64_bit)
 
+# Some third-party code bases depend on this being set for big-endians.
+set_define(
+    "WORDS_BIGENDIAN", True, when=depends(target.endianness)(lambda e: e == "big")
+)
+
 
 # Autoconf needs these set