cmake: support make and make install

(2nd attempt to get this right)

cmake/install.cmake

@@ -0,0 +1,37 @@
+message("-- Installing: ${CMAKE_INSTALL_PREFIX}/lib")
+
+if(NOT EXISTS ${zig0_EXE})
+    message("::")
+    message(":: ERROR: Executable not found")
+    message(":: (execute_process)")
+    message("::")
+    message(":: executable: ${zig0_EXE}")
+    message("::")
+    message(FATAL_ERROR)
+endif()
+
+execute_process(COMMAND ${zig0_EXE} ${INSTALL_LIBUSERLAND_ARGS}
+    WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+    RESULT_VARIABLE _result
+)
+if(_result)
+    message("::")
+    message(":: ERROR: ${_result}")
+    message(":: (execute_process)")
+
+    string(REPLACE ";" " " s_INSTALL_LIBUSERLAND_ARGS "${INSTALL_LIBUSERLAND_ARGS}")
+    message("::")
+    message(":: argv: ${zig0_EXE} ${s_INSTALL_LIBUSERLAND_ARGS} install")
+
+    set(_args ${zig0_EXE} ${INSTALL_LIBUSERLAND_ARGS})
+    list(LENGTH _args _len)
+    math(EXPR _len "${_len} - 1")
+    message("::")
+    foreach(_i RANGE 0 ${_len})
+        list(GET _args ${_i} _arg)
+        message(":: argv[${_i}]: ${_arg}")
+    endforeach()
+
+    message("::")
+    message(FATAL_ERROR)
+endif()