diff -rupN qt3d-everywhere-src-5.12.3/src/3rdparty/assimp/assimp.pri qt3d-everywhere-src-5.12.3-new/src/3rdparty/assimp/assimp.pri
--- qt3d-everywhere-src-5.12.3/src/3rdparty/assimp/assimp.pri	2019-04-03 06:16:06.000000000 +0200
+++ qt3d-everywhere-src-5.12.3-new/src/3rdparty/assimp/assimp.pri	2019-04-18 11:29:41.832474008 +0200
@@ -6,7 +6,9 @@ CONFIG -= precompile_header
 
 win32:DEFINES+=_CRT_SECURE_NO_WARNINGS
 
-qtConfig(system-zlib):!if(cross_compile:host_build): \
+cross_compile {
+    LIBS += -lz
+} else: qtConfig(system-zlib):!if(cross_compile:host_build): \
     QMAKE_USE_PRIVATE += zlib
 else: \
     QT_PRIVATE += zlib-private