economy.cpp's compilation is quite long

[flomnes]

47s on my machine, with a single active process.

time /usr/lib/gcc/x86_64-linux-gnu/9/cc1plus -quiet
-I /home/omnesflo/Antares_Simulator/src/ext/yuni/src
-I /home/omnesflo/Antares_Simulator/src/libs
-I /home/omnesflo/Antares_Simulator/src/libs/antares/logs
-I /home/omnesflo/Antares_Simulator/src/solver/writer
-imultiarch
x86_64-linux-gnu
-MD CMakeFiles/libantares-solver-main-economy.dir/economy.cpp.d
-MF CMakeFiles/libantares-solver-main-economy.dir/economy.cpp.o.d
-MT solver/main/CMakeFiles/libantares-solver-main-economy.dir/economy.cpp.o
-D _GNU_SOURCE
-D NDEBUG
-D _REENTRANT
-D XUSE_MTSAFE_API
/home/omnesflo/Antares_Simulator/src/solver/main/economy.cpp
-quiet
-dumpbase
economy.cpp
-msse
-msse2
-mtune=generic
-march=x86-64
-auxbase-strip
CMakeFiles/libantares-solver-main-economy.dir/economy.cpp.o
-O3
-O3
-Werror=return-type
-Wall
-Wextra
-Wfatal-errors
-Wunused-but-set-variable
-Wunused-but-set-parameter
-Werror=return-type
-std=gnu++17
-funroll-loops
-finline-functions
-fvisibility-inlines-hidden
-fasynchronous-unwind-tables
-fstack-protector-strong
-Wformat-security
-fstack-clash-protection
-fcf-protection

Surely the build can be made faster, but how ?