scripts: add BUILD/HOST extra cflags/ldflags

On some hosts, and for certain toolchains (eg. toolchain targetting
the upcoming Darwin), it may be necessary to pass arbitrary CFLAGS
and/or LDFLAGS when building the components.

And necessary infrastructure:
- EXTRA_{CFLAGS,LDFLAGS}_FOR_{BUILD,HOST} as config options
- pass those extra flags to components

Fix-up a slight typo in elf2flt at the same time (misnamed cflags).

Signed-off-by: Yann Diorcet <diorcet.yann@gmail.com>
Message-Id: <d24043276c9243a35421.1353077450@macbook-smorlat.local>
Patchwork-Id: 199645

# This file declares functions to install the kernel headers for mingw64

# Copyright 2012 Yann Diorcet

# Licensed under the GPL v2. See COPYING in the root of this package

CT_DoKernelTupleValues() {

    # Even we compile for x86_64 target architecture, the target OS have to

    # bet mingw32 (require by gcc and mingw-w64)

    CT_TARGET_KERNEL="mingw32"

    CT_TARGET_SYS=

}

do_kernel_get() {

    :

}

do_kernel_extract() {

    :

}

do_kernel_headers() {

   :

}