[core] mason geojsonvt-2.1.6.3

- [osx] set -fvisibility-inlines-hidden in gyp/common.gypi to silence
  mismatched visibility linker warnings
- [linux] set cxx_host in GYP_FLAGS to set -fabi-version=0 on gcc builds
  to use clang-built mason binaries
- [ios] update symbol visibility for iOS tests
- [ios] link libgeojsonvt.a in iOS tests xcodeproj
  - add libgeojsonvt.a to General -> Linked Frameworks and Libraries
  - add mason_packages (recursive) to Build Settings -> Library Search Path
- [ios] add libuv and geojsonvt first in iOS libtool smush to ensure symbols
  are found by later compilation units where they are undefined

scripts/linux/configure.sh

@@ -11,6 +11,7 @@ LIBUV_VERSION=1.7.5
 ZLIB_VERSION=system
 NUNICODE_VERSION=1.6
 LIBZIP_VERSION=1.0.1
+GEOJSONVT_VERSION=2.1.6.3
 VARIANT_VERSION=1.0
 RAPIDJSON_VERSION=1.0.2
 GTEST_VERSION=1.7.0