meson: disable subprocess command for fuzzing

Allowing arbitrary command execution for the fuzzer is not ideal. While
some testing of this code is valid, unsupervised fuzzing of the input is
not. It may be better to add a dedicated test or fuzz-test for this
case.

meson.build

@@ -414,7 +414,7 @@ endif
 
 if posix
     path_source = files('osdep/path-unix.c')
-    if cc.has_function('fork', prefix : '#include <unistd.h>')
+    if not get_option('fuzzers') and cc.has_function('fork', prefix : '#include <unistd.h>')
         sources += files('osdep/subprocess-posix.c')
     else
         sources += files('osdep/subprocess-dummy.c')
@@ -516,9 +516,13 @@ if features['win32-desktop']
                           cc.find_library('version')]
     dependencies += win32_desktop_libs
     path_source = files('osdep/path-win.c')
+    if not get_option('fuzzers')
+        sources += files('osdep/subprocess-win.c')
+    else
+        sources += files('osdep/subprocess-dummy.c')
+    endif
     sources += files('input/ipc-win.c',
                      'osdep/language-win.c',
-                     'osdep/subprocess-win.c',
                      'osdep/terminal-win.c',
                      'video/out/w32_common.c',
                      'video/out/win32/displayconfig.c',