Setup cmake project

Add the top level cmake project and ninja and gn cmake builds.
Make ninja and gn build optional.

With qmake we had four stages during the build:

  * configure (initial dependencies check)
  * qmake (build ninja, build gn, run gn)
  * make (compilation)
  * make install

With cmake we have some limitations:

  a) we need to pass the build config to gn, however cmake
    evaluates generator expressions during the generation phase
    this means we need a recursive call to cmake
  b) qt-cmake qtbase logic (+syncqt) assumes "fixed" build locations
    to handle deployment of headers and libs (it uses
    CMAKE_BINARY_DIR for QT_BUILD_DIR)
  c) cmake can not run twice in the same build directory
  d) running recursive/child cmake, makes all generated targets not
    accessible during configure time of parent's cmake
  e) cmake can only "build" things for subdirectories

To deal with mentioned limitations and to keep things simple we will
split those steps into separate projects:

  * SUPERBUILD - this project does dependency checks, only evaluates features
    to show the build summary and passes them to EXAMPLES,LIBS,TESTS
    projects, it also runs the generator expression to feed LIBS project's
    cmake, it does not try to run syncqt as result of (b) and (c)
  * NINJA (build ninja)
  * GN (build gn)
  * LIBS - projects runs simplified feature evaluation (CONDITIONS
    resolved by SUPERBUILD cmake) to generate build headers (+syncqt),
    it also runs gn during configure and does all libs
    compilation. The project's source root must be "src" directory
    as a result of (a),(b),(c)
  * EXAMPLES - builds examples as a result of (d),(e)
  * TESTS - builds tests as a result of (d),(e)

Each of projects will have three stages: configure, compile, install.

Task-number: QTBUG-91760
Done-With: Jüri Valdmann <juri.valdmann@qt.io>
Change-Id: I3b44decefa17f177e5e07c563796aa158a0b0ecb
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>

2 files changed, 54 insertions, 0 deletions

diff --git a/cmake/FindGn.cmake b/cmake/FindGn.cmake
new file mode 100644
index 000000000..dfbe5b363
--- /dev/null
+++ b/cmake/FindGn.cmake
@@ -0,0 +1,23 @@
+if (NOT DEFINED WEBENGINE_ROOT_BUILD_DIR)
+    set(WEBENGINE_ROOT_BUILD_DIR  ${CMAKE_CURRENT_BINARY_DIR}/../..)
+endif()
+
+set(CMAKE_PROGRAM_PATH ${WEBENGINE_ROOT_BUILD_DIR}/install/bin)
+find_program(Gn_EXECUTABLE NAMES gn)
+
+include(FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args(
+    Gn
+    REQUIRED_VARS Gn_EXECUTABLE)
+
+if(Gn_FOUND AND NOT TARGET Gn::gn)
+    add_executable(Gn::gn IMPORTED)
+    set_property(TARGET Gn::gn PROPERTY IMPORTED_LOCATION ${Gn_EXECUTABLE})
+endif()
+
+include(FeatureSummary)
+set_package_properties(Gn PROPERTIES
+    URL "https://gn.googlesource.com/gn/"
+    DESCRIPTION "Meta-build system"
+)
diff --git a/cmake/FindNinja.cmake b/cmake/FindNinja.cmake
new file mode 100644
index 000000000..3615d58b9
--- /dev/null
+++ b/cmake/FindNinja.cmake
@@ -0,0 +1,31 @@
+if (NOT DEFINED WEBENGINE_ROOT_BUILD_DIR)
+    set(WEBENGINE_ROOT_BUILD_DIR  ${CMAKE_CURRENT_BINARY_DIR}/..)
+endif()
+
+set(CMAKE_PROGRAM_PATH ${WEBENGINE_ROOT_BUILD_DIR}/install/bin)
+find_program(Ninja_EXECUTABLE NAMES ninja ninja-build)
+
+if(Ninja_EXECUTABLE)
+    execute_process(
+        COMMAND ${Ninja_EXECUTABLE} --version
+        OUTPUT_VARIABLE Ninja_VERSION
+        ERROR_QUIET
+        OUTPUT_STRIP_TRAILING_WHITESPACE)
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(
+    Ninja
+    REQUIRED_VARS Ninja_EXECUTABLE
+    VERSION_VAR Ninja_VERSION)
+
+if(Ninja_FOUND AND NOT TARGET Ninja::ninja)
+    add_executable(Ninja::ninja IMPORTED)
+    set_property(TARGET Ninja::ninja PROPERTY IMPORTED_LOCATION ${Ninja_EXECUTABLE})
+endif()
+
+include(FeatureSummary)
+set_package_properties(Ninja PROPERTIES
+    URL "https://ninja-build.org/"
+    DESCRIPTION "Build tool"
+)