Implement separate compile flags per module/file

[salkinium]

This implements adding separate compile flags for specific files by attaching metadata to lbuild operations. This allows to compile CMSIS-DSP with its own flags (specifically __FPU_PRESENT=1 is required), without using these settings globally (which triggers a warning since <stm32xx.h> device headers usually define this macro).

Implemented for:

• SCons
• CMake

See #125 for discussion.
Depends on modm-io/lbuild#16.
cc @dergraaf @rleh @se-bi @chris-durand

[salkinium]

Unfortunately the generated SConscript files now gets a little more verbose:

files = [
    env.File("ext/tlsf/tlsf.c"),
    # ...
    env.File("src/modm/utils/dummy.cpp"),
]
flags = {"CFLAGS": ['$CFLAGS', '-fno-strict-aliasing'], "CPPDEFINES": ['$CPPDEFINES', 'ARM_MATH_ROUNDING', 'UNALIGNED_SUPPORT_DISABLE', '__FPU_PRESENT=1'], }
if profile == "debug": flags["CPPDEFINES"].extend(['ARM_MATH_MATRIX_CHECK']);
files.append(env.Object("ext/cmsis/dsp/BasicMathFunctions/arm_abs_f32.c", **flags))
flags = {"CFLAGS": ['$CFLAGS', '-fno-strict-aliasing'], "CPPDEFINES": ['$CPPDEFINES', 'ARM_MATH_ROUNDING', 'UNALIGNED_SUPPORT_DISABLE', '__FPU_PRESENT=1'], }
if profile == "debug": flags["CPPDEFINES"].extend(['ARM_MATH_MATRIX_CHECK']);
files.append(env.Object("ext/cmsis/dsp/BasicMathFunctions/arm_abs_q15.c", **flags))
# ... for all cmsis-dsp files