Simplify CMake mruby object library

Also removes an unnecessary build target from the CMake generated
build and project files.

src/CMakeLists.txt

@@ -7,6 +7,5 @@ file(GLOB MRUBY_SRC_C "*.c")
 list(APPEND MRUBY_SRC_C "${CMAKE_CURRENT_BINARY_DIR}/parse.c")
 
 add_library(mruby_object OBJECT ${MRUBY_SRC_C} ${BISON_mruby_OUTPUTS})
-add_library(mruby_static STATIC EXCLUDE_FROM_ALL $<TARGET_OBJECTS:mruby_object>)
 
 # vim: ts=2 sts=2 sw=2 et

tools/mrbc/CMakeLists.txt

 # build tools/mrbc executable
 
 file(GLOB MRBC_SRC_C "*.c")
-add_executable(mrbc ${MRBC_SRC_C})
-target_link_libraries(mrbc mruby_static ${MRUBY_LIBS})
+add_executable(mrbc ${MRBC_SRC_C} $<TARGET_OBJECTS:mruby_object>)
+target_link_libraries(mrbc ${MRUBY_LIBS})
 
 install(TARGETS mrbc RUNTIME DESTINATION bin)