cmake: Prefix all options with "SDL_"

This makes it clear which options came from SDL's CMake project when
building SDL as a subdirectory of a parent CMake project.

Fixes #4139.

build-scripts/checker-buildbot.sh

@@ -27,7 +27,7 @@ cd checker-buildbot
 # The -Wno-liblto is new since our checker-279 upgrade, I think; checker otherwise warns "libLTO.dylib relative to clang installed dir not found"
 
 # You might want to do this for CMake-backed builds instead...
-scan-build -o analysis cmake -G Ninja -Wno-dev -DSDL_STATIC=OFF -DCMAKE_BUILD_TYPE=Debug -DASSERTIONS=enabled -DCMAKE_C_FLAGS="-Wno-deprecated-declarations" -DCMAKE_SHARED_LINKER_FLAGS="-Wno-liblto" ..
+scan-build -o analysis cmake -G Ninja -Wno-dev -DSDL_STATIC=OFF -DCMAKE_BUILD_TYPE=Debug -DSDL_ASSERTIONS=enabled -DCMAKE_C_FLAGS="-Wno-deprecated-declarations" -DCMAKE_SHARED_LINKER_FLAGS="-Wno-liblto" ..
 
 # ...or run configure without the scan-build wrapper...
 #CC="$CHECKERDIR/libexec/ccc-analyzer" CFLAGS="-O0 -Wno-deprecated-declarations" LDFLAGS="-Wno-liblto" ../configure --enable-assertions=enabled

build-scripts/codechecker-buildbot.sh

@@ -24,7 +24,7 @@ mkdir codechecker-buildbot
 cd codechecker-buildbot
 
 # We turn off deprecated declarations, because we don't care about these warnings during static analysis.
-cmake -Wno-dev -DSDL_STATIC=OFF -DCMAKE_BUILD_TYPE=Debug -DASSERTIONS=enabled -DCMAKE_C_FLAGS="-Wno-deprecated-declarations" -DCMAKE_EXPORT_COMPILE_COMMANDS=1 ..
+cmake -Wno-dev -DSDL_STATIC=OFF -DCMAKE_BUILD_TYPE=Debug -DSDL_ASSERTIONS=enabled -DCMAKE_C_FLAGS="-Wno-deprecated-declarations" -DCMAKE_EXPORT_COMPILE_COMMANDS=1 ..
 
 # CMake on macOS adds "-arch arm64" or whatever is appropriate, but this confuses CodeChecker, so strip it out.
 perl -w -pi -e 's/\-arch\s+.*?\s+//g;' compile_commands.json

cmake/macros.cmake

@@ -42,12 +42,18 @@ macro(MESSAGE_TESTED_OPTION _NAME)
   if(${ARGC} EQUAL 2)
     set(_PAD ${ARGV1})
   endif()
-  if(NOT HAVE_${_NAME})
-    set(HAVE_${_NAME} OFF)
-  elseif("${HAVE_${_NAME}}" MATCHES "1|TRUE|YES|Y")
-    set(HAVE_${_NAME} ON)
+  string(SUBSTRING "${_NAME}" 0 4 _NAMESTART)
+  if(_NAMESTART STREQUAL "SDL_")
+    string(SUBSTRING "${_NAME}" 4 -1 _STRIPPEDNAME)
+  else()
+    set(_STRIPPEDNAME "${_NAME}")
   endif()
-  message(STATUS "  ${_NAME}${_PAD}(Wanted: ${_REQVALUE}): ${HAVE_${_NAME}}")
+  if(NOT HAVE_${_STRIPPEDNAME})
+    set(HAVE_${_STRIPPEDNAME} OFF)
+  elseif("${HAVE_${_STRIPPEDNAME}}" MATCHES "1|TRUE|YES|Y")
+    set(HAVE_${_STRIPPEDNAME} ON)
+  endif()
+  message(STATUS "  ${_NAME}${_PAD}(Wanted: ${_REQVALUE}): ${HAVE_${_STRIPPEDNAME}}")
 endmacro()
 
 macro(LISTTOSTR _LIST _OUTPUT)