Describe the bug
A clear and concise description of what the bug is.

Environment

• OS: Windows
• Compiler: Visual studio 2019

To Reproduce
Steps to reproduce the behavior:

1. ./vcpkg install boost
2. See error
   Additional packages (*) will be modified to complete this operation.
   Detecting compiler hash for triplet x86-windows...
   Starting package 1/90: bzip2:x86-windows
   Building package bzip2[core]:x86-windows...
   Could not locate cached archive: C:\Users\sp\AppData\Local\vcpkg\archives\ca\ca870ac55962fdf2d70d629065a53de5e6be0169.zip
   -- Using cached E:/github/cxx/vcpkg/downloads/bzip2-1.0.6.tar.gz
   -- Cleaning sources at E:/github/cxx/vcpkg/buildtrees/bzip2/src/1.0.6-8838f21f8e.clean. Use --editable to skip cleaning for the packages you specify.
   -- Extracting source E:/github/cxx/vcpkg/downloads/bzip2-1.0.6.tar.gz
   -- Applying patch fix-import-export-macros.patch
   -- Applying patch fix-windows-include.patch
   -- Using source at E:/github/cxx/vcpkg/buildtrees/bzip2/src/1.0.6-8838f21f8e.clean
   -- Configuring x86-windows
   -- Building x86-windows-dbg
   -- Building x86-windows-rel
   -- Fixing pkgconfig
   CMake Error at scripts/cmake/vcpkg_fixup_pkgconfig.cmake:279 (find_program):
   Could not find PKGCONFIG using the following names: pkg-config
   Call Stack (most recent call first):
   ports/bzip2/portfile.cmake:51 (vcpkg_fixup_pkgconfig)
   scripts/ports.cmake:79 (include)

Error: Building package bzip2:x86-windows failed with: BUILD_FAILED
Please ensure you're using the latest portfiles with .\vcpkg update, then
submit an issue at https://github.com/Microsoft/vcpkg/issues including:
Package: bzip2:x86-windows
Vcpkg version: 2020.06.15-nohash

Additionally, attach any relevant sections from the log files above.

at scripts/cmake/vcpkg_fixup_pkgconfig.cmake:279
find_program(PKGCONFIG pkg-config PATHS "bin" "/usr/bin" "/usr/local/Cellar/pkg-config/0.29.2_3" REQUIRED)

use REQUIRED will not goto vcpkg_acquire_msys to get msys

if(NOT PKGCONFIG)
find_program(PKGCONFIG pkg-config PATHS "bin" "/usr/bin" "/usr/local/Cellar/pkg-config/0.29.2_3" REQUIRED)
if(NOT PKGCONFIG AND CMAKE_HOST_WIN32)
vcpkg_acquire_msys(MSYS_ROOT PACKAGES pkg-config)
find_program(PKGCONFIG pkg-config PATHS "${MSYS_ROOT}/usr/bin" REQUIRED)
endif()
debug_message("Using pkg-config from: ${PKGCONFIG}")
if(NOT PKGCONFIG AND NOT _vfpkg_SKIP_CHECK)
message(WARNING "Unable to find pkg-config to validate *.pc files. Skipping checkes!")
set(_vfpkg_SKIP_CHECK TRUE)
endif()
endif()