diff -up thunderbird-45.3.0/mozilla/old-configure.in.no_Os thunderbird-45.3.0/mozilla/configure.in
--- thunderbird-45.3.0/mozilla/old-configure.in.no_Os	2016-08-30 16:29:23.611672500 +0200
+++ thunderbird-45.3.0/mozilla/old-configure.in	2016-08-30 16:29:51.520620404 +0200
@@ -2115,7 +2115,7 @@ ia64*-hpux*)
 *-*linux*)
     if test "$GNU_CC" -o "$GNU_CXX"; then
         MOZ_PGO_OPTIMIZE_FLAGS="-O3"
-        MOZ_OPTIMIZE_FLAGS="-Os"
+        MOZ_OPTIMIZE_FLAGS=""
         if test -z "$CLANG_CC"; then
            MOZ_OPTIMIZE_FLAGS="-freorder-blocks $MOZ_OPTIMIZE_FLAGS"
         fi