cmake: wire up initial support

The project uses a Makefile as the build system for the test executable.
This makes it hard to build and test on Windows via MSVC.

Introduce support for CMake.

.gitignore

@@ -0,0 +1 @@
+/build/

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.25.0)
+
+project(clar LANGUAGES C)
+
+option(BUILD_TESTS "Build test executable" ON)
+
+add_library(clar INTERFACE)
+target_sources(clar INTERFACE
+	clar.c
+	clar.h
+	clar/fixtures.h
+	clar/fs.h
+	clar/print.h
+	clar/sandbox.h
+	clar/summary.h
+)
+set_target_properties(clar PROPERTIES
+	C_STANDARD 90
+	C_STANDARD_REQUIRED ON
+	C_EXTENSIONS OFF
+)
+
+if(BUILD_TESTS)
+	add_subdirectory(test)
+endif()

test/CMakeLists.txt

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+find_package(Python COMPONENTS Interpreter REQUIRED)
+
+add_custom_command(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/clar.suite"
+	COMMAND "${Python_EXECUTABLE}" "${CMAKE_SOURCE_DIR}/generate.py" --output "${CMAKE_CURRENT_BINARY_DIR}"
+	DEPENDS main.c sample.c
+	WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+)
+
+add_executable(clar_test)
+set_target_properties(clar_test PROPERTIES
+	C_STANDARD 90
+	C_STANDARD_REQUIRED ON
+	C_EXTENSIONS OFF
+)
+
+# MSVC generates all kinds of warnings. We may want to fix these in the future
+# and then unconditionally treat warnings as errors.
+if (NOT MSVC)
+	set_target_properties(clar_test PROPERTIES
+		COMPILE_WARNING_AS_ERROR ON
+	)
+endif()
+
+target_sources(clar_test PRIVATE
+	main.c
+	sample.c
+	"${CMAKE_CURRENT_BINARY_DIR}/clar.suite"
+)
+target_compile_definitions(clar_test PRIVATE
+	CLAR_FIXTURE_PATH="${CMAKE_CURRENT_SOURCE_DIR}/resources/"
+	_DARWIN_C_SOURCE
+	_POSIX_C_SOURCE=200809L
+)
+target_compile_options(clar_test PRIVATE
+	$<IF:$<CXX_COMPILER_ID:MSVC>,/W4,-Wall>
+)
+target_include_directories(clar_test PRIVATE
+	"${CMAKE_SOURCE_DIR}"
+	"${CMAKE_CURRENT_BINARY_DIR}"
+)
+target_link_libraries(clar_test clar)