Add option to override build type

- glog_bench in Release configuration produces better results on Windows

external/README.md

@@ -15,27 +15,30 @@ On a prompt, run the following
 git submodule update --init
 cmake -P build_and_run.cmake
 ```
-Optionally, the CMake generator can be overridden using `-DGenerator=<generator name>`.
-Ensure it goes before `-P`.
+Optionally:
+- The build configuration can be overridden using `-DConfiguration=<config name>`. Use `Release` on Windows for better results.
+- The CMake generator can be overridden using `-DGenerator=<generator name>`. Use `Ninja` for faster builds.
+
+Ensure these go before `-P`.
 
 The cmake script builds Gflags, Glog and the dependent test projects: glog_bench and glog_example.
 After the build process, it runs the test projects and shows the relevant output.
 #### Sample result
 ```
 running T:/GitRepo/loguru/external/build/glog_bench;ERROR_QUIET
-LOG(WARNING) << string (buffered): 73.695 +- 1.548 us per call
-LOG(WARNING) << float  (buffered): 83.216 +- 0.986 us per call
-LOG(WARNING) << string (unbuffered): 79.280 +- 2.453 us per call
-LOG(WARNING) << float  (unbuffered): 87.755 +- 0.762 us per call
+LOG(WARNING) << string (buffered): 29.347 +- 0.303 us per call
+LOG(WARNING) << float  (buffered): 31.816 +- 0.103 us per call
+LOG(WARNING) << string (unbuffered): 31.926 +- 0.139 us per call
+LOG(WARNING) << float  (unbuffered): 34.603 +- 0.136 us per call
 running T:/GitRepo/loguru/external/build/glog_example
-I1231 14:49:09.042631  4020 glog_example.cpp:10] Hello from main.cpp!
-I1231 14:49:09.044632  4020 glog_example.hpp:14] complex_calculation started
-I1231 14:49:09.044632  4020 glog_example.hpp:15] Starting time machine...
-W1231 14:49:09.245019  4020 glog_example.hpp:17] The flux capacitor is not getting enough power!
-I1231 14:49:09.646394  4020 glog_example.hpp:19] Lighting strike!
-E1231 14:49:10.047559 10976 glog_example.hpp:23] We ended up in 1985!
-I1231 14:49:10.048560  4020 glog_example.hpp:25] complex_calculation stopped
-I1231 14:49:10.048560  4020 glog_example.cpp:12] main function about to end!
+I1231 17:03:14.299798  8852 glog_example.cpp:10] Hello from T:\GitRepo\loguru\external\test\glog_example.cpp!
+I1231 17:03:14.301300  8852 glog_example.hpp:14] complex_calculation started
+I1231 17:03:14.301300  8852 glog_example.hpp:15] Starting time machine...
+W1231 17:03:14.501893  8852 glog_example.hpp:17] The flux capacitor is not getting enough power!
+I1231 17:03:14.902706  8852 glog_example.hpp:19] Lighting strike!
+E1231 17:03:15.303464  7036 glog_example.hpp:23] We ended up in 1985!
+I1231 17:03:15.303964  8852 glog_example.hpp:25] complex_calculation stopped
+I1231 17:03:15.303964  8852 glog_example.cpp:12] main function about to end!
 ```
 There are various environment-dependent variables in the result. YMMV.
 

external/build_and_run.cmake

@@ -10,9 +10,13 @@ macro(EXEC_CMD_CHECK)
   endif()
 endmacro()
 
-# pass in command-line to override the default generator (ex. -DGenerator=Ninja)
+# to override the default configuration: ex. -DConfiguration=Release
+if(DEFINED Configuration)
+  list(APPEND CMAKE_EXTRA_ARGS -DCMAKE_BUILD_TYPE=${Configuration})
+endif()
+# to override the default generator: ex. -DGenerator=Ninja
 if(DEFINED Generator)
-  set(CMAKE_GENERATOR_ARG "-G${Generator}")
+  list(APPEND CMAKE_EXTRA_ARGS "-G${Generator}")
 endif()
 
 set(BUILD_DIR ${CMAKE_CURRENT_LIST_DIR}/build)
@@ -26,10 +30,13 @@ set(BUILD_DIR ${CMAKE_CURRENT_LIST_DIR}/build)
 EXEC_CMD_CHECK(${CMAKE_COMMAND} -E make_directory ${BUILD_DIR})
 
 # cd build && cmake .. && cd -
-EXEC_CMD_CHECK(${CMAKE_COMMAND} ${CMAKE_GENERATOR_ARG} ${CMAKE_CURRENT_LIST_DIR} WORKING_DIRECTORY ${BUILD_DIR})
+EXEC_CMD_CHECK(${CMAKE_COMMAND} ${CMAKE_EXTRA_ARGS} ${CMAKE_CURRENT_LIST_DIR} WORKING_DIRECTORY ${BUILD_DIR})
 
+if(DEFINED Configuration)
+  set(CMAKE_BUILD_EXTRA_ARGS --config ${Configuration})
+endif()
 # platform-independent equivalent of `make`
-EXEC_CMD_CHECK(${CMAKE_COMMAND} --build ${BUILD_DIR})
+EXEC_CMD_CHECK(${CMAKE_COMMAND} --build ${BUILD_DIR} ${CMAKE_BUILD_EXTRA_ARGS})
 
 # ./glog_bench 2>/dev/null
 EXEC_CMD_CHECK(${BUILD_DIR}/glog_bench ERROR_QUIET)