feat(megbrain): add mc20 cmake

GitOrigin-RevId: 4d64e803fbd8e45bf7b56a41ee818b8d576bea4d

cmake/mc20.cmake

+find_path(MC20_ROOT_DIR
+    include/ax_interpreter_external_api.h
+    PATHS
+    ${PROJECT_SOURCE_DIR}/third_party/mc20/
+    $ENV{MC20DIR}
+)
+
+if(${MC20_ROOT_DIR} STREQUAL "MC20_ROOT_DIR-NOTFOUND")
+    message(FATAL_ERROR "Can not find MC20")
+endif()
+message(STATUS "Build with MC20 in ${MC20_ROOT_DIR}")
+
+find_path(MC20_INCLUDE_DIR
+    ax_interpreter_external_api.h
+    PATHS
+    ${MC20_ROOT_DIR}/include
+    ${INCLUDE_INSTALL_DIR}
+)
+
+add_library(libmc20 INTERFACE IMPORTED)
+find_library(MC20_LIBRARY
+    NAMES libax_interpreter_external.x86.a
+    PATHS ${MC20_ROOT_DIR}/lib/)
+
+if(${MC20_LIBRARY} STREQUAL "MC20_LIBRARY-NOTFOUND")
+    message(FATAL_ERROR "Can not find MC20 library")
+endif()
+target_link_libraries(libmc20 INTERFACE ${MC20_LIBRARY})
+target_include_directories(libmc20 INTERFACE ${MC20_INCLUDE_DIR})