build: Add -Wtrailing-whitespace=any compiler flag

CMakeLists.txt

@@ -224,6 +224,7 @@ else()
   try_append_c_flags(-Wreserved-identifier) # Clang >= 13.0 only.
   try_append_c_flags(-Wshadow)
   try_append_c_flags(-Wstrict-prototypes)
+  try_append_c_flags(-Wtrailing-whitespace=any) # GCC >= 15.0
   try_append_c_flags(-Wundef)
 endif()
 

configure.ac

@@ -111,6 +111,7 @@ AC_DEFUN([SECP_TRY_APPEND_DEFAULT_CFLAGS], [
       SECP_TRY_APPEND_CFLAGS([-Wcast-align=strict], $1) # GCC >= 8.0
       SECP_TRY_APPEND_CFLAGS([-Wconditional-uninitialized], $1) # Clang >= 3.0 only
       SECP_TRY_APPEND_CFLAGS([-Wreserved-identifier], $1) # Clang >= 13.0 only
+      SECP_TRY_APPEND_CFLAGS([-Wtrailing-whitespace=any], $1) # GCC >= 15.0
 
       CFLAGS="$SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS"
     fi

src/checkmem.h

@@ -78,10 +78,15 @@
 #  if defined(__clang__) && defined(__APPLE__)
 #    pragma clang diagnostic push
 #    pragma clang diagnostic ignored "-Wreserved-identifier"
+#  elif defined(__GNUC__) && (__GNUC__ >= 15)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wtrailing-whitespace"
 #  endif
 #    include <valgrind/memcheck.h>
 #  if defined(__clang__) && defined(__APPLE__)
 #    pragma clang diagnostic pop
+#  elif defined(__GNUC__) && (__GNUC__ >= 15)
+#    pragma GCC diagnostic pop
 #  endif
 #    define SECP256K1_CHECKMEM_ENABLED 1
 #    define SECP256K1_CHECKMEM_UNDEFINE(p, len) VALGRIND_MAKE_MEM_UNDEFINED((p), (len))