Посмотрите на system-configuration-options
переменную.
Вот пример, который является результатом запуска C-h v system-configuration-options
system-configuration-options is a variable defined in `C source code'.
Its value is
"--prefix=/usr/local/emacs 'CFLAGS=-O2 -march=native -pipe
-falign-functions=64 -fomit-frame-pointer -ftracer -funit-at-a-time
-fweb -fforce-addr -fpeel-loops -funswitch-loops -frename-registers
-mfpmath=sse -ffast-math -fno-finite-math-only -fstack-check'
PKG_CONFIG_PATH=/usr/share/pkgconfig"
Documentation:
String containing the configuration options Emacs was built with.
For more information check the manuals.