cmake PortGroup: don't add -I${prefix}/include to CXXFLAGS

[mojca (Mojca Miklavec)]

CMake is automatically fed with too many (too early) includes of $prefix/include:

CPPFLAGS='-I/opt/local/include'
CFLAGS='-pipe -Os -I/opt/local/include -arch x86_64'
CXXFLAGS='-pipe -Os -I/opt/local/include -arch x86_64'

with the following explanation in the PortGroup:

# The environment variable CPPFLAGS is not considered by CMake.
# (CMake upstream ticket #12928 "CMake silently ignores CPPFLAGS"
# <http://www.cmake.org/Bug/view.php?id=12928>).
# Thus, we have to add them manually to the CFLAGS and CXXFLAGS in the
# pre-configure phase.
if {${configure.cppflags} ne ""} {
    configure.cflags-append ${configure.cppflags}
    configure.cxxflags-append ${configure.cppflags}
}

As a consequence the CMake-based installations have problems when function definitions change in an upgrade. I don't know if I should blame the developers for that or not. (In case of CLHEP, the ./configure-based installation puts -I. in front of CPPFLAGS, so headers from sources are found first, but in CMake-based installation -I. comes later.)

We should check whether we could use ​CMAKE_INCLUDE_PATH (-DCMAKE_INCLUDE_PATH=${prefix}/include) instead of configure.cxxflags-append ${configure.cppflags} for example.

See also:

• ​https://savannah.cern.ch/bugs/index.php?103664 (and ticket #42613)
• ​http://www.cmake.org/Wiki/CMake_Useful_Variables