cmake: fix quotes in configure_runtime

[junghans]

Fix for #3158 (comment)

/usr/bin/gmake  -f CMakeFiles/configure_runtime.dir/build.make CMakeFiles/configure_runtime.dir/depend
gmake[2]: Entering directory '/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build'
cd /builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /builddir/build/BUILD/lfortran-0.31.0 /builddir/build/BUILD/lfortran-0.31.0 /builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build /builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build /builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build/CMakeFiles/configure_runtime.dir/DependInfo.cmake --color=
gmake[2]: Leaving directory '/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build'
/usr/bin/gmake  -f CMakeFiles/configure_runtime.dir/build.make CMakeFiles/configure_runtime.dir/build
gmake[2]: Entering directory '/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build'
cd /builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build/src/runtime && /usr/bin/cmake -G\ Unix\ Makefiles -DCMAKE_TOOLCHAIN_FILE= -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH="/usr/lib64/llvm16/" -DCMAKE_INSTALL_LIBDIR=lib64 -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON -DCMAKE_Fortran_COMPILER=/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build/src/bin/lfortran -DLFORTRAN_NESTED_BUILD=yes /builddir/build/BUILD/lfortran-0.31.0/src/runtime/
CMake Error: Could not create named generator  Unix Makefiles
Generators
  Green Hills MULTI            = Generates Green Hills MULTI files
                                 (experimental, work-in-progress).
* Unix Makefiles               = Generates standard UNIX makefiles.
  Ninja                        = Generates build.ninja files.
  Ninja Multi-Config           = Generates build-<Config>.ninja files.
  Watcom WMake                 = Generates Watcom WMake makefiles.
  CodeBlocks - Ninja           = Generates CodeBlocks project files.
  CodeBlocks - Unix Makefiles  = Generates CodeBlocks project files.
  CodeLite - Ninja             = Generates CodeLite project files.
  CodeLite - Unix Makefiles    = Generates CodeLite project files.
  Eclipse CDT4 - Ninja         = Generates Eclipse CDT 4.0 project files.
  Eclipse CDT4 - Unix Makefiles= Generates Eclipse CDT 4.0 project files.
  Kate - Ninja                 = Generates Kate project files.
  Kate - Unix Makefiles        = Generates Kate project files.
  Sublime Text 2 - Ninja       = Generates Sublime Text 2 project files.
  Sublime Text 2 - Unix Makefiles
                               = Generates Sublime Text 2 project files.
gmake[2]: Leaving directory '/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build'
gmake[1]: Leaving directory '/builddir/build/BUILD/lfortran-0.31.0/redhat-linux-build'
gmake[2]: *** [CMakeFiles/configure_runtime.dir/build.make:73: CMakeFiles/configure_runtime] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:393: CMakeFiles/configure_runtime.dir/all] Error 2
gmake: *** [Makefile:169: all] Error 2