Adding configure option: -no-gcc-sysroot

Adding configure option: -no-gcc-sysroot

This option is important if you want to use configure's
and qmake's -sysroot (e.g. PKG_CONFIG settings, device-files),
but the toolchain (in combination with the rootfs)
is not able to handle gcc's --sysroot.
One known case is freescale's ltib setup where the toolchain
itself comes with all the essential files (e.g. crt1.o),
while the rootfs has none of those files, so gcc's
--sysroot can't be used. The rootfs on the other hand contains
all kinds of "less important" files/packages (e.g. libdbus).
For those "less important" files/packages Qt needs pkg-config
to be able to include/link properly. Therefore one needs
configures -sysroot without gcc's --sysroot.

Change-Id: Iaec9b07012f2945f3ecb3ced0ed95176721b5ecd
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>