cmake: enable `-std=gnu99` for Windows CE CeGCC

To sync with autotools, which auto-detects this option and enables it by
default.

It also makes it possible to compile unsuffixed long long integer
literals correctly, allowing to drop some legacy macros without bumping
into build errors like:
```
lib/vtls/schannel.c: In function 'schannel_send':
lib/vtls/schannel.c:1815: error: integer constant is too large for 'long' type
```
Ref: https://github.com/curl/curl/actions/runs/15374705821/job/43286736583?pr=17498#step:9:20

Bug: https://github.com/curl/curl/pull/17498#issuecomment-2925507481
Reported-by: Daniel Stenberg
Closes #17523

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f82b4d900f0bd84a5b9944850a11addb11132aa4..825577e2e83d0ff9971db62fe94ad019bd016b2d 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -88,6 +88,10 @@ elseif(WIN32 AND WINCE AND CMAKE_C_COMPILER_ID STREQUAL "GNU")  # mingw32ce buil
   set(CMAKE_RC_COMPILE_OBJECT "<CMAKE_RC_COMPILER> -O coff <DEFINES> <INCLUDES> <FLAGS> <SOURCE> <OBJECT>")
   enable_language(RC)
 
+  # To compile long long integer literals
+  set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "-std=gnu99")
+  string(APPEND CMAKE_REQUIRED_FLAGS " -std=gnu99")
+
   set(CMAKE_C_COMPILE_OPTIONS_PIC "")  # CMake sets it to '-fPIC', confusing the toolchain and breaking builds. Zap it.
 
   set(CMAKE_STATIC_LIBRARY_PREFIX "lib")