pkg-cmake: fix host-cmake-package type

When trying to compile a host-cmake-package type such as host-cdrkit,
an error happens in regards to HOSTCC and HOSTCXX not being found.

  /bin/sh: HOSTCC: command not found
  /bin/sh: HOSTCXX: command not found

This due to the fact that the environment is incorrectly configured by
having the following:

  -DCMAKE_C_COMPILER=""$(HOSTCC)"" -DCMAKE_CXX_COMPILER=""$(HOSTCXX)""

This is due to having too many dollar signs. The fix is to remove the
extra dollar sign.

Also removing the unncessary quotes since the HOSTCC/HOSTCXX will
already contain quotes. This could cause an issue with make as double
quotes are not interpreted by make.

Minor formatting fix too.

Signed-off-by: Ryan Barnett <ryan.barnett@rockwellcollins.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>