CMake: Implement configure -optimize-size

This configure switch controls the feature 'optimize_size'.

This isn't merely a mapping to CMAKE_BUILD_TYPE=MinSizeRel, because
we potentially want to combine -optimize-size with -force-debug-info,
which maps to CMAKE_BUILD_CONFIG=RelWithDebInfo.

Task-number: QTBUG-85373
Change-Id: I1a9343ebc54816f52e90e9d33ea3df4c99b1ec9f
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtFlagHandlingHelpers.cmake

@@ -361,6 +361,11 @@ function(qt_internal_set_up_config_optimizations_like_in_qmake)
                 string(APPEND "${flag_var_name}" " ${QT_CFLAGS_OPTIMIZE_DEBUG}")
             endif()
 
+            set(configs_for_optimize_size RELEASE RELWITHDEBINFO)
+            if(QT_FEATURE_optimize_size AND config IN_LIST configs_for_optimize_size)
+                string(APPEND "${flag_var_name}" " ${QT_CFLAGS_OPTIMIZE_SIZE}")
+            endif()
+
             # Assign value to the cache entry.
             get_property(help_text CACHE "${flag_var_name}" PROPERTY HELPSTRING)
             set("${flag_var_name}" "${${flag_var_name}}" CACHE STRING "${help_text}" FORCE)

cmake/configure-cmake-mapping.md

@@ -28,7 +28,7 @@ The effort of this is tracked in QTBUG-85373 and QTBUG-85349.
 | -debug-and-release                    | -G "Ninja Multi-Config"                           |                                                                 |
 |                                       | -DCMAKE_CONFIGURATION_TYPES=Release;Debug         |                                                                 |
 | -optimize-debug                       | -DFEATURE_optimize_debug=ON                       |                                                                 |
-| -optimize-size                        |                                                   |                                                                 |
+| -optimize-size                        | -DFEATURE_optimize_size=ON                        |                                                                 |
 | -optimized-tools                      | n/a                                               | This affects only host tools.                                   |
 | -force-debug-info                     | Use the RelWithDebInfo build config.              |                                                                 |
 | -separate-debug-info                  | -DFEATURE_separate_debug_info=ON                  |                                                                 |

configure.cmake

@@ -415,6 +415,12 @@ qt_feature("optimize_debug"
     CONDITION NOT MSVC AND NOT CLANG AND ( QT_FEATURE_debug OR QT_FEATURE_debug_and_release ) AND TEST_optimize_debug
 )
 qt_feature_config("optimize_debug" QMAKE_PRIVATE_CONFIG)
+qt_feature("optimize_size"
+    LABEL "Optimize release build for size"
+    AUTODETECT OFF
+    CONDITION NOT QT_FEATURE_debug OR QT_FEATURE_debug_and_release
+)
+qt_feature_config("optimize_size" QMAKE_PRIVATE_CONFIG)
 qt_feature("pkg-config" PUBLIC
     LABEL "Using pkg-config"
     AUTODETECT NOT APPLE AND NOT WIN32

util/cmake/configurejson2cmake.py

@@ -897,7 +897,6 @@ def get_feature_mapping():
         "incredibuild_xge": None,
         "ltcg": {"autoDetect": "1", "condition": "CMAKE_INTERPROCEDURAL_OPTIMIZATION"},
         "msvc_mp": None,
-        "optimize_size": None,
         "simulator_and_device": {"condition": "UIKIT AND NOT QT_UIKIT_SDK"},
         "pkg-config": {"condition": "PKG_CONFIG_FOUND"},
         "precompile_header": {"condition": "BUILD_WITH_PCH"},