Let breakpad build with -Wall on OS X and Linux.

src/common/linux/synth_elf.cc

Index: src/common/linux/synth_elf.cc
diff --git a/src/common/linux/synth_elf.cc b/src/common/linux/synth_elf.cc
index b978550f85e5fda3248067d92f382f58171e1d21..98e81dab7523bce97cb075231f80dd96294c9be9 100644
--- a/src/common/linux/synth_elf.cc
+++ b/src/common/linux/synth_elf.cc
@@ -213,8 +213,10 @@ void ELF::Finish() {
 SymbolTable::SymbolTable(Endianness endianness,
                          size_t addr_size,
                          StringTable& table) : Section(endianness),
-                                               addr_size_(addr_size),
                                                table_(table) {
+#ifndef NDEBUG
+  addr_size_ = addr_size;
+#endif
   assert(addr_size_ == 4 || addr_size_ == 8);
 }