Fix fan monitor custom_target break

The recent meson format commit reordered arguments of some custom_target
calls, where the code expected the first input to be the script being
run.  Hardcode that argument instead.

The presence/control versions were already fixed, this just fixes the
monitor one.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Iea849d9b69336ee0dcf3379b467b3d01ba4e7607
diff --git a/monitor/meson.build b/monitor/meson.build
index 28cd3ab..3baba85 100644
--- a/monitor/meson.build
+++ b/monitor/meson.build
@@ -23,13 +23,11 @@
 
 # Only needed for YAML config
 if get_option('json-config').disabled()
+    script = files('gen-fan-monitor-defs.py')
     fan_monitor_defs_cpp_dep = custom_target(
         'fan_monitor_defs.cpp',
-        input: files(
-            conf.get_unquoted('FAN_MONITOR_YAML_FILE'),
-            './gen-fan-monitor-defs.py',
-        ),
-        command: [python_prog, '@INPUT0@', '-m', '@INPUT1@', '-o', 'monitor'],
+        input: files(conf.get_unquoted('FAN_MONITOR_YAML_FILE')),
+        command: [python_prog, script, '-m', '@INPUT0@', '-o', 'monitor'],
         output: 'fan_monitor_defs.cpp',
     )