build: Remove libv4l2 dependency from meson

We use the linux/v4l2-common.h header to access v4l devices, not libv4l from v4l-utils.

meson.build

@@ -151,7 +151,8 @@ endif
 
 openhmd = dependency('openhmd', required: openhmd_required)
 hidapi  = dependency('hidapi-libusb', required: hidapi_required)
-v4l2    = dependency('libv4l2', required: v4l2_required)
+
+has_v4l2_header =  cc.has_header('linux/v4l2-common.h')
 
 if openhmd.found() and ('auto' in drivers or 'ohmd' in drivers)
 	if 'ohmd' not in drivers
@@ -177,7 +178,7 @@ if rs.found() and ('auto' in drivers or 'rs' in drivers)
 	endif
 endif
 
-if v4l2.found() and ('auto' in drivers or 'v4l2' in drivers)
+if has_v4l2_header and ('auto' in drivers or 'v4l2' in drivers)
 	if 'v4l2' not in drivers
 		drivers += ['v4l2']
 	endif

src/xrt/drivers/meson.build

@@ -113,7 +113,7 @@ lib_drv_v4l2 = static_library(
 		'v4l2/v4l2_driver.c',
 	),
 	include_directories: xrt_include,
-	dependencies: [aux, v4l2],
+	dependencies: [aux],
 	build_by_default: 'v4l2' in drivers,
 )
 

src/xrt/include/xrt/meson.build

@@ -65,7 +65,7 @@ if sdl2.found()
 	have_conf.set('XRT_HAVE_SDL2', true)
 endif
 
-if v4l2.found() and 'v4l2' in drivers
+if has_v4l2_header and 'v4l2' in drivers
 	have_conf.set('XRT_HAVE_V4L2', true)
 endif
 

src/xrt/state_trackers/prober/meson.build

@@ -27,10 +27,6 @@ if libuvc.found()
 	prober_deps += [libuvc]
 endif
 
-if v4l2.found()
-	prober_deps += [v4l2]
-endif
-
 lib_st_prober = static_library(
 	'st_prober',
 	files(prober_sources),

src/xrt/targets/meson.build

@@ -47,7 +47,6 @@ endif
 
 if 'v4l2' in drivers
 	driver_libs += [lib_drv_v4l2]
-	driver_deps += [v4l2]
 endif
 
 if 'vive' in drivers