cmake.bbclass: add HOSTTOOLS_DIR to CMAKE_FIND_ROOT_PATH
The find_program command will fail if it is used on a tool that is listed in
ASSUME_PROVIDED. This is because these tools are in the hosttools directory
which is not listed in CMAKE_FIND_ROOT_PATH so cmake will not find them.
Adding the directory HOSTTOOLS_DIR to the CMAKE_FIND_ROOT_PATH variable fixes
the initial issue of needing to search for tools in ASSUME_PROVIDED.
Note that this change alone does not fix the issue because find_program will
by default only look into the subdirectories bin and usr/bin under the paths
in CMAKE_FIND_ROOT_PATH to find the programs and the hosttools directory has
instead the symlinks directly present without these subdirectories.
Set CMAKE_PROGRAM_PATH to by default include the root directory so
find_program can search the hosttools directory without needing the prefix
directories.
Signed-off-by: Ross Burton <ross.burton@intel.com>
