Bug 1478923 - Remove LLVM_SYMBOLIZER from mozconfig.lto. r=froydnj

This was cargo-culted from the asan/tsan mozconfigs, but is not necessary
for builds without sanitizers.

--HG--
extra : rebase_source : 41bad4761f424410cb7a099ecaecce8a86becf59

build/unix/mozconfig.lto

@@ -9,7 +9,6 @@ export RANLIB="$topsrcdir/clang/bin/llvm-ranlib"
 
 export CC="$topsrcdir/clang/bin/clang"
 export CXX="$topsrcdir/clang/bin/clang++"
-export LLVM_SYMBOLIZER="$topsrcdir/clang/bin/llvm-symbolizer"
 
 # Use a newer binutils, from the tooltool gcc package, if it's there
 if [ -e "$topsrcdir/gcc/bin/ld" ]; then