Wasm: Build with Qt's freetype, png and zlib

Compilation breaks on Windows and macOS hosts with USE_ZLIB=1.

In addition, it turns out that the versions of the libraries in
Emscripten Ports are outdated. Since we have newer versions
of these libraries in Qt already, we will just use those.

This is a revert of 70b558ad5b.

Task-number: QTQAINFRA-2835
Change-Id: Ic2642b7d319a3447fd08843657eb0535255e0449
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

mkspecs/wasm-emscripten/qmake.conf

@@ -32,15 +32,6 @@ EMCC_COMMON_LFLAGS = \
     --bind \
     -s \"BINARYEN_TRAP_MODE=\'clamp\'\"
 
-EMCC_USE_PORTS_FLAGS = \
-    -s USE_FREETYPE=1 \
-    -s USE_ZLIB=1
-
-# libpng does not build for WASM_OBJECT_FILES=1, see
-# https://github.com/emscripten-core/emscripten/issues/8143
-equals(WASM_OBJECT_FILES, 0):\
-    EMCC_USE_PORTS_FLAGS += -s USE_LIBPNG=1
-
 # The -s arguments can also be used with release builds,
 # but are here in debug for clarity.
 EMCC_COMMON_LFLAGS_DEBUG = \
@@ -87,9 +78,6 @@ QMAKE_COMPILER         += emscripten
 QMAKE_CC                = emcc
 QMAKE_CXX               = em++
 
-QMAKE_CFLAGS           += $$EMCC_USE_PORTS_FLAGS
-QMAKE_CXXFLAGS         += $$EMCC_USE_PORTS_FLAGS
-
 QMAKE_LINK              = $$QMAKE_CXX
 QMAKE_LINK_SHLIB        = $$QMAKE_CXX
 QMAKE_LINK_C            = $$QMAKE_CC