Enable automatic generation of compile_flags.txt for clang-tidy via make tidy (#2008)

.gitignore

@@ -11,6 +11,7 @@
 *.gcno
 *.gcda
 *.gcov
+/compile_flags.txt
 CMakeCache.txt
 CMakeFiles/
 cmake_install.cmake

Makefile

@@ -33,11 +33,13 @@ WARNFLAGS := -Wall -pedantic -Wno-unknown-warning-option \
 # Overridable CXXFLAGS
 CXXFLAGS     ?= -O3 -flto -DNDEBUG
 # Non-overridable CXXFLAGS
-REALCXXFLAGS := ${CXXFLAGS} ${WARNFLAGS} -std=c++20 -I include -fno-exceptions -fno-rtti
+REQUIREDCXXFLAGS := -std=c++20 -I include -fno-exceptions -fno-rtti
+REALCXXFLAGS := ${CXXFLAGS} ${WARNFLAGS} ${REQUIREDCXXFLAGS}
 # Overridable LDFLAGS
 LDFLAGS      ?=
 # Non-overridable LDFLAGS
-REALLDFLAGS  := ${LDFLAGS} ${WARNFLAGS} -DBUILD_VERSION_STRING=\"${VERSION_STRING}\"
+REQUIREDLDFLAGS := -DBUILD_VERSION_STRING=\"${VERSION_STRING}\"
+REALLDFLAGS  := ${LDFLAGS} ${WARNFLAGS} ${REQUIREDLDFLAGS}
 
 # Wrapper around bison that passes flags depending on what the version supports
 BISON := src/bison.sh
@@ -250,8 +252,10 @@ format:
 
 # Target used in development to check code with clang-tidy.
 # Requires Bison-generated header files to exist.
-tidy: src/asm/parser.hpp src/link/script.hpp
+tidy: src/asm/parser.hpp src/link/script.hpp compile_flags.txt
 	$Qclang-tidy -p . $$(git ls-files '*.[hc]pp')
+compile_flags.txt:
+	$Qprintf '%s\n' ${REQUIREDCXXFLAGS} ${REQUIREDLDFLAGS} >$@
 
 # Target used in development to remove unused `#include` headers.
 iwyu:

compile_flags.txt

@@ -1,6 +0,0 @@
--std=c++20
--I
-include
--fno-exceptions
--fno-rtti
--fno-caret-diagnostics

docs/ARCHITECTURE.md

@@ -65,7 +65,6 @@ rgbds/
 ├── .clang-tidy
 ├── CMakeLists.txt
 ├── CMakePresets.json
-├── compile_flags.txt
 ├── Dockerfile
 └── Makefile
 ```
@@ -129,8 +128,6 @@ rgbds/
   Defines how to build RGBDS with CMake.
 - **`CMakePresets.json`:**  
   Defines some [presets](https://cmake.org/cmake/help/latest/manual/cmake-presets.7.html) useful for working with our CMake.
-- **`compile_flags.txt`:**  
-  Compiler flags for `clang-tidy`.
 - **`Dockerfile`:**  
   Defines how to build RGBDS with Docker (which we do in CI to provide a [container image](https://github.com/gbdev/rgbds/pkgs/container/rgbds)).
 - **`Makefile`:**