msdk: Fixes for meson include directory setup

In case of pkg-config we need to create the include directories object
from the path using include_directories(). For INTELMEDIASDKROOT or
MFX_HOME we need to add the alternate include path ./include/mfx as
Intel MediaSDK now puts the headers there.
24 jobs for master in 61 minutes and 38 seconds (queued for 10 seconds)
latest
Status Job ID Name Coverage
  Preparation
passed #897478
gst indent

00:00:32

passed #897477
manifest

00:00:31

 
  Build
passed #897488
build cerbero cross-android universal

00:09:42

manual #897492
gst-ios-12.2 allowed to fail manual
build cerbero cross-ios universal
passed #897489
build cerbero cross win32

00:04:40

passed #897490
build cerbero cross win64

00:03:45

passed #897487
build cerbero fedora x86_64

00:04:32

passed #897491
gst-macos-10.14
build cerbero macos x86_64

00:06:13

passed #897483
build clang fedora x86_64

00:04:59

passed #897479
build fedora x86_64

00:03:38

passed #897486
docker windows 1607
build msys2

00:12:05

passed #897480
build nodebug fedora x86_64

00:02:26

passed #897481
build static fedora x86_64

00:11:30

passed #897482
build static nodebug fedora x86_64

00:04:00

passed #897499
docker windows 1607
build vs2017 amd64

00:10:23

passed #897485
docker windows 1607
build vs2017 x86

00:09:57

failed #897484
docker windows 1607
build vs2017 amd64

00:00:07

 
  Test
passed #897889
check fedora

00:03:31

passed #897494
integration testsuites fedora

00:39:48

passed #897495
valgrind bad

00:09:18

failed #897493
check fedora

00:03:59

 
  Integrate
passed #897496
cross-android universal examples

00:07:43

manual #897498
gst-ios-12.2 allowed to fail manual
cross-ios universal examples
passed #897497
documentation

00:04:23