package/lirc-tools: use single quote with SETUPTOOLS_ENV

package/lirc-tools: use single quote with SETUPTOOLS_ENV

With the change to pkg-python to use TARGET_CONFIGURE_OPTS in
PKG_PYTHON_SETUPTOOLS_ENV in commit 1745fcde74, the
LIRC_TOOLS_MAKE_ENV is incorrect as it sets the SETUPTOOLS_ENV using
double quotes. This causes issues because the
PKG_PYTHON_SETUPTOOLS_ENV contain double quotes as well. This causes a
build error such as:

  /bin/sh: -I/home/naourr/work/instance-0/output-1/host/include
          CXXFLAGS_FOR_BUILD=-O2: No such file or directory

Fix this by using single quotes with PKG_PYTHON_SETUPTOOLS_ENV instead
of double quotes.

Fixes:
  http://autobuild.buildroot.net/results/f7a9c02add9bde563c7289f7c0be2cb7aefd96b8

Signed-off-by: Ryan Barnett <ryan.barnett@rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>