GNU linker: Use single-argument form of --dependency-file flag

The GNU `ld(1)` manual documents the `--dependency-file=depfile`
single-argument form of the flag.  Prefer it over the multi-argument
`--dependency-file depfile` form so that only one argument needs to be
passed through the compiler driver by `-Wl,` or equivalent.  This may
improve diagnostics in cases where it is unsupported, making them easier
to diagnose.

Issue: #26483

Modules/Linker/GNU.cmake

@@ -11,7 +11,7 @@ cmake_policy(SET CMP0140 NEW)
 
 function(__linker_gnu lang)
   # define flags for linker depfile generation
-  set(CMAKE_${lang}_LINKER_DEPFILE_FLAGS "LINKER:--dependency-file,<DEP_FILE>")
+  set(CMAKE_${lang}_LINKER_DEPFILE_FLAGS "LINKER:--dependency-file=<DEP_FILE>")
   set(CMAKE_${lang}_LINKER_DEPFILE_FORMAT gcc)
 
   if(NOT CMAKE_EXECUTABLE_FORMAT STREQUAL "ELF")