Stop defaulting to the "RelWithDebInfo" build type

The Nixpkgs build environment i.a. expects CMAKE_BUILD_TYPE to be an
empty string (which would set no optimization flags).

.gitignore

@@ -1,2 +1,5 @@
 /.eldev
 /Eldev-local
+
+/build
+/hotfuzz-module.so

CMakeLists.txt

@@ -1,17 +1,10 @@
 cmake_minimum_required(VERSION 3.19)
 project(hotfuzz C)
 
-if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
-  message(STATUS "Setting build type to 'RelWithDebInfo' as none was specified.")
-  set(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE
-	STRING "Choose the type of build." FORCE)
-endif()
-
-find_program(EMACS_PROGRAM emacs)
-if(EMACS_PROGRAM)
-  get_filename_component(EMACS_PROGRAM ${EMACS_PROGRAM} REALPATH)
-  get_filename_component(EMACS_PROGRAM_DIR ${EMACS_PROGRAM} DIRECTORY)
-  get_filename_component(EMACS_PROGRAM_DIR ${EMACS_PROGRAM_DIR} DIRECTORY)
+find_program(EMACS_EXECUTABLE emacs)
+if(EMACS_EXECUTABLE)
+  file(REAL_PATH ${EMACS_EXECUTABLE} EMACS_EXECUTABLE)
+  set(EMACS_PROGRAM_DIR ${EMACS_EXECUTABLE}/../..)
 endif()
 
 find_path(EMACS_INCLUDE_DIR emacs-module.h
@@ -26,8 +19,8 @@ find_package(Threads REQUIRED)
 add_library(hotfuzz-module MODULE hotfuzz-module.c)
 set_target_properties(hotfuzz-module PROPERTIES
   C_STANDARD 11
-  POSITION_INDEPENDENT_CODE ON
+  C_STANDARD_REQUIRED ON
   PREFIX ""
   LIBRARY_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR})
-target_include_directories(hotfuzz-module PRIVATE ${EMACS_INCLUDE_DIR})
+target_include_directories(hotfuzz-module SYSTEM PRIVATE ${EMACS_INCLUDE_DIR})
 target_link_libraries(hotfuzz-module PRIVATE Threads::Threads)

README.md

@@ -55,8 +55,8 @@ and run
 ```sh
 mkdir build
 cd build
-cmake -DCMAKE_C_FLAGS='-O3 -march=native' .. \
-	&& cmake --build .
+cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_FLAGS=-march=native .. &&
+	cmake --build .
 ```
 
 and place the resulting shared library somewhere in `load-path`.