message: [platform-expression] add freebsd and openbsd
diff: @@ -26,6 +26,8 @@ namespace vcpkg::PlatformExpression
  windows,
  mingw,
  linux,
  + freebsd,
  + openbsd,
  osx,
  uwp,
  android,
  @@ -50,6 +52,8 @@ namespace vcpkg::PlatformExpression
  {"windows", Identifier::windows},
  {"mingw", Identifier::mingw},
  {"linux", Identifier::linux},
  + {"freebsd", Identifier::freebsd},
  + {"openbsd", Identifier::openbsd},
  {"osx", Identifier::osx},
  {"uwp", Identifier::uwp},
  {"android", Identifier::android},
  @@ -537,6 +541,8 @@ namespace vcpkg::PlatformExpression
  true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "MinGW");
  case Identifier::mingw: return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "MinGW");
  case Identifier::linux: return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "Linux");
  + case Identifier::freebsd: return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "FreeBSD");
  + case Identifier::openbsd: return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "OpenBSD");
  case Identifier::osx: return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "Darwin");
  case Identifier::uwp:
  return true_if_exists_and_equal("VCPKG_CMAKE_SYSTEM_NAME", "WindowsStore");
  