CMakeLists.txt
-------------

cmake_minimum_required(VERSION 2.6)

PROJECT(CompilerFlags)

ADD_EXECUTABLE(CompilerFlags CompilerFlags.cxx)

list(APPEND myvariable "UNIX")
list(APPEND myvariable "DAVID")
message("myvariable: " ${myvariable})
set_target_properties(CompilerFlags PROPERTIES COMPILE_DEFINITIONS "${myvariable}") #note, must have quotes around variable

make VERBOSE=1 output
-------------------

/usr/bin/cmake -H/media/portable/Examples/CMake/CompilerFlags -B/media/portable/Examples/CMake/CompilerFlags/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/media/portable/Examples/CMake/CompilerFlags/build'
make -f CMakeFiles/CompilerFlags.dir/build.make CMakeFiles/CompilerFlags.dir/depend
make[2]: Entering directory `/media/portable/Examples/CMake/CompilerFlags/build'
cd /media/portable/Examples/CMake/CompilerFlags/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /media/portable/Examples/CMake/CompilerFlags /media/portable/Examples/CMake/CompilerFlags /media/portable/Examples/CMake/CompilerFlags/build /media/portable/Examples/CMake/CompilerFlags/build /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles/CompilerFlags.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/media/portable/Examples/CMake/CompilerFlags/build'
make -f CMakeFiles/CompilerFlags.dir/build.make CMakeFiles/CompilerFlags.dir/build
make[2]: Entering directory `/media/portable/Examples/CMake/CompilerFlags/build'
/usr/bin/cmake -E cmake_progress_report /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles 1
[100%] Building CXX object CMakeFiles/CompilerFlags.dir/CompilerFlags.cxx.o
/usr/lib/ccache/c++   -DUNIX -DDAVID -g   -o CMakeFiles/CompilerFlags.dir/CompilerFlags.cxx.o -c /media/portable/Examples/CMake/CompilerFlags/CompilerFlags.cxx
Linking CXX executable CompilerFlags
/usr/bin/cmake -E cmake_link_script CMakeFiles/CompilerFlags.dir/link.txt --verbose=1
/usr/lib/ccache/c++   -g   CMakeFiles/CompilerFlags.dir/CompilerFlags.cxx.o  -o CompilerFlags -rdynamic 
make[2]: Leaving directory `/media/portable/Examples/CMake/CompilerFlags/build'
/usr/bin/cmake -E cmake_progress_report /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles  1
[100%] Built target CompilerFlags
make[1]: Leaving directory `/media/portable/Examples/CMake/CompilerFlags/build'
/usr/bin/cmake -E cmake_progress_start /media/portable/Examples/CMake/CompilerFlags/build/CMakeFiles 0