Build specific example using -DBUILD_EXAMPLE cmake flag (#3921)

CMakeLists.txt

@@ -59,7 +59,10 @@ if(NOT TARGET uninstall)
     COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
 endif()
 
-if (${BUILD_EXAMPLES})
+if (NOT ${BUILD_EXAMPLE} STREQUAL "")
+  MESSAGE(STATUS "Building example '${BUILD_EXAMPLE}'")
+  add_subdirectory(examples)
+elseif (${BUILD_EXAMPLES})
   MESSAGE(STATUS "Building examples is enabled")
   add_subdirectory(examples)
 endif()

CMakeOptions.txt

@@ -8,6 +8,7 @@ enum_option(OPENGL_VERSION "OFF;4.3;3.3;2.1;1.1;ES 2.0;ES 3.0" "Force a specific
 
 # Configuration options
 option(BUILD_EXAMPLES "Build the examples." ${RAYLIB_IS_MAIN})
+option(BUILD_EXAMPLE "Build a specific example by filename." "")
 option(CUSTOMIZE_BUILD "Show options for customizing your Raylib library build." OFF)
 option(ENABLE_ASAN  "Enable AddressSanitizer (ASAN) for debugging (degrades performance)" OFF)
 option(ENABLE_UBSAN "Enable UndefinedBehaviorSanitizer (UBSan) for debugging" OFF)

examples/CMakeLists.txt

@@ -48,10 +48,24 @@ endif ()
 # into a CMake variable
 set(example_sources)
 set(example_resources)
+set(example_found FALSE)
 foreach (example_dir ${example_dirs})
-    # Get the .c files
-    file(GLOB sources ${example_dir}/*.c)
-    list(APPEND example_sources ${sources})
+    if (BUILD_EXAMPLE)
+        if (NOT example_found)
+            file(GLOB sources ${example_dir}/${BUILD_EXAMPLE}.c)
+            if (EXISTS ${sources})
+                list(APPEND example_sources ${sources})
+                set(example_found TRUE)
+                message("Raylib example '${BUILD_EXAMPLE}.c' found in ${example_dir}!")
+            else()
+                message("Raylib example '${BUILD_EXAMPLE}.c' not found in ${example_dir}...")
+            endif()
+        endif()
+    else()
+        # Get the .c files
+        file(GLOB sources ${example_dir}/*.c)
+        list(APPEND example_sources ${sources})
+    endif()
 
     # Any any resources
     file(GLOB resources ${example_dir}/resources/*)