vpx: Error out if enabled and no features found

Seee: gstreamer/cerbero#200
24 jobs for error-vpx-no-features in 66 minutes and 12 seconds (queued for 21 seconds)
Status Job ID Name Coverage
  Preparation
passed #887479
gst indent

00:00:30

passed #887478
manifest

00:00:32

 
  Build
passed #887489
build cerbero cross-android universal

00:08:19

manual #887493
gst-ios-12.2 allowed to fail manual
build cerbero cross-ios universal
passed #887490
build cerbero cross win32

00:07:39

passed #887491
build cerbero cross win64

00:05:01

passed #887488
build cerbero fedora x86_64

00:05:40

passed #887492
gst-macos-10.14
build cerbero macos x86_64

00:06:20

passed #887484
build clang fedora x86_64

00:06:07

passed #887480
build fedora x86_64

00:07:10

passed #887487
1607 windows docker
build msys2

00:13:17

passed #887481
build nodebug fedora x86_64

00:03:01

passed #887482
build static fedora x86_64

00:12:16

passed #887483
build static nodebug fedora x86_64

00:03:16

passed #887485
1607 windows docker
build vs2017 amd64

00:11:45

passed #887486
1607 windows docker
build vs2017 x86

00:11:06

 
  Test
passed #887494
check fedora

00:04:04

passed #887495
integration testsuites fedora

00:41:47

passed #887497
valgrind bad

00:11:08

passed #887498
valgrind ges

00:07:49

passed #887496
valgrind good

00:10:12

 
  Integrate
passed #887499
cross-android universal examples

00:09:05

manual #887501
gst-ios-12.2 allowed to fail manual
cross-ios universal examples
passed #887500
documentation

00:04:19