set python executable var to custom cmake commands (#3)

Author: knmcguire

rosidl_generator_rs/cmake/custom_command.cmake

@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+find_package(Python3 REQUIRED COMPONENTS Interpreter)
+set(PYTHON_EXECUTABLE ${Python3_EXECUTABLE})
+
 add_custom_command(
  OUTPUT
  ${_generated_common_rs_files}