doc: add pkg-config requirement for applications
doc: add pkg-config requirement for applications

DPDK relies on pkg-config(1) to provide correct parameters for
compiler and linker used in application build.  Inaccurate build
parameters, produced by pkg-config from DPDK .pc files could fail
application build or cause unpredicted results during application
runtime.

Update system requirements doc about a bug in pkg-config v0.27
used in RHEL-7.

Signed-off-by: Gregory Etelson <3a519118dcb518b0e040298252dc92c436a7335f@nvidia.com>
Signed-off-by: Thomas Monjalon <5f50a84c1fa3bcff146405017f36aec1a10a9e38@monjalon.net>
Acked-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk