Bug 1474488 - add --enable-undefined-sanitizer (mainly for fuzzing interface). r=nfroyd

browser/config/mozconfigs/linux64/nightly-asan

@@ -10,6 +10,10 @@ ac_add_options --enable-valgrind
 . $topsrcdir/build/unix/mozconfig.asan
 ac_add_options --disable-elf-hack
 
+# Piggybacking UBSan for now since only a small subset of checks are enabled.
+# A new build can be created when appropriate.
+ac_add_options --enable-undefined-sanitizer
+
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 

browser/config/mozconfigs/linux64/nightly-fuzzing-asan

@@ -18,6 +18,10 @@ ac_add_options --disable-elf-hack
 ac_add_options --enable-fuzzing
 unset MOZ_STDCXX_COMPAT
 
+# Piggybacking UBSan for now since only a small subset of checks are enabled.
+# A new build can be created when appropriate.
+ac_add_options --enable-undefined-sanitizer
+
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1