windows build fixes

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "src/ext/openexr"]
 	path = src/ext/openexr
 	url = https://github.com/wjakob/openexr
+[submodule "src/ext/zlib"]
+	path = src/ext/zlib
+	url = https://github.com/mitsuba-renderer/zlib

CMakeLists.txt

@@ -95,6 +95,18 @@ ELSE()
     )
 ENDIF()
 
+IF(WIN32)
+  # Build zlib (only on Windows)
+  SET(ZLIB_BUILD_STATIC_LIBS ON CACHE BOOL " " FORCE)
+  SET(ZLIB_BUILD_SHARED_LIBS OFF CACHE BOOL " " FORCE)
+  ADD_SUBDIRECTORY(src/ext/zlib)
+
+  SET(ZLIB_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/src/ext/zlib")
+  SET(ZLIB_LIBRARY "${CMAKE_CURRENT_BINARY_DIR}/src/ext/zlib/$<CONFIGURATION>/zlibstatic.lib")
+  SET_PROPERTY(TARGET zlibstatic PROPERTY FOLDER "dependencies")
+  INCLUDE_DIRECTORIES(${ZLIB_INCLUDE_DIR} "${CMAKE_CURRENT_BINARY_DIR}/src/ext/zlib")
+ENDIF()
+
 SET(ILMBASE_NAMESPACE_VERSIONING OFF CACHE BOOL " " FORCE)
 SET(OPENEXR_NAMESPACE_VERSIONING OFF CACHE BOOL " " FORCE)
 SET(OPENEXR_BUILD_SHARED_LIBS    OFF CACHE BOOL " " FORCE)
@@ -218,6 +230,14 @@ ADD_LIBRARY ( pbrt STATIC
   ${PBRT_SOURCE}
   )
 
+IF (WIN32)
+  # Avoid a name clash when building on Visual Studio
+  SET_TARGET_PROPERTIES ( pbrt
+    PROPERTIES
+    OUTPUT_NAME libpbrt
+    )
+ENDIF()
+
 FIND_PACKAGE ( Threads )
 
 # Main renderer