Another way to check is to enter about:buildconfig in the address bar and then press enter. I see
Code:
about:buildconfig
Source
Built from http://hg.mozilla.org/releases/mozilla-release/rev/e8bb3550be0f344804a13cc7aa268b91a9154e93
Build platform
target
x86_64-unknown-linux-gnu
Build tools
Compiler Version Compiler flags
/usr/bin/ccache /builds/slave/rel-c-rel-lnx64-bld/build/gcc/bin/gcc 4.7.3 -Wall -Wempty-body -Wpointer-to-int-cast -Wsign-compare -Wtype-limits -Wno-unused -Wcast-align -std=gnu99 -fgnu89-inline -fno-strict-aliasing -ffunction-sections -fdata-sections -fno-math-errno -pthread -pipe
/usr/bin/ccache /builds/slave/rel-c-rel-lnx64-bld/build/gcc/bin/g++ 4.7.3 -Wall -Wempty-body -Woverloaded-virtual -Wsign-compare -Wwrite-strings -Wno-invalid-offsetof -Wcast-align -fno-exceptions -fno-strict-aliasing -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -fno-math-errno -std=gnu++0x -pthread -D_GLIBCXX_USE_CXX11_ABI=0 -pipe -DNDEBUG -DTRIMMED -g -freorder-blocks -Os -fomit-frame-pointer
Configure arguments
--enable-crashreporter --enable-release --enable-elf-hack --enable-stdcxx-compat --enable-default-toolkit=cairo-gtk2 --enable-application=suite --enable-optimize --enable-update-channel=release --enable-update-packaging --disable-debug --enable-tests --with-ccache=/usr/bin/ccache --with-external-source-dir=/builds/slave/rel-c-rel-lnx64-bld/build
I used https://archive.mozilla.org/pub/mozi...x86_64.tar.bz2 as the source and installed it locally.