We want compiler check arguments (-O0, -fpermissive, etc) to override
all other arguments, and we want extra_args passed in by the build file
to always override everything.
To do this properly, we must split include arguments out, append them
first, append all other arguments as usual, and then append the rest.
As part of this, we also add the compiler check flags to the
cc.compiles() and cc.links() helper functions since they also most
likely need them.
Also includes a unit test for all this.
We now use .links() to detect if a C compiler function is available
or not, that way the user doesn't need to specify all the possible
includes for the check, which simplifies things considerably.
Also detect glibc stub functions that will never work and return
false for them.
Closes#437
Nirbheek Chauhan
Nirbheek Chauhan
Tim-Philipp Müller
Jussi Pakkanen