Try to make builds reproducible

Reproducible builds for neovim-qt are not working because mapping flags
passed to the cmake build are included in the code (through version.h.in).
Meaning that builds with slightly different mapping flags end up being
different; even if no other compiler flags are different.

ref #1111

Adds build option for reproducible builds. Currently only affects the use
of compilation flags in the --version output.

CMakeLists.txt

@@ -10,6 +10,7 @@ endif()
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+option(REPRODUCIBLE_BUILD "Make this build reproducible" OFF)
 option(USE_GCOV "Enable gcov support" OFF)
 option(ENABLE_CLAZY "Build with KDE Clang Clazy Linter" OFF)
 option(ENABLE_TIDY "Build with Clang Tidy Linter" OFF)

src/gui/app.cpp

@@ -446,7 +446,9 @@ void App::showVersionInfo(QCommandLineParser& parser) noexcept
 
 	out << "NVIM-QT v" << PROJECT_VERSION << QT_ENDL;
 	out << "Build type: " << CMAKE_BUILD_TYPE << QT_ENDL;
+#if !defined(REPRODUCIBLE_BUILD)
 	out << "Compilation:" << CMAKE_CXX_FLAGS << QT_ENDL;
+#endif
 	out << "Qt Version: " << QT_VERSION_STR << QT_ENDL;
 	out << "Environment: " << QT_ENDL;
 	out << "  nvim: " << nvimExecutable << QT_ENDL;

src/version.h.in

@@ -16,7 +16,10 @@
 #define RC_PROJECT_NAME "@PROJECT_NAME@\0"
 #define RC_PROJECT_VERSION "@PROJECT_VERSION@\0"
 
+#cmakedefine REPRODUCIBLE_BUILD
+#if !defined(REPRODUCIBLE_BUILD)
 #define CMAKE_CXX_FLAGS "@CMAKE_CXX_FLAGS@"
+#endif
 #define CMAKE_BUILD_TYPE "@CMAKE_BUILD_TYPE@"
 
 #endif // NEOVIM_QT_VERSION