diff --git a/extlib/libpng/CMakeLists.txt b/extlib/libpng/CMakeLists.txt
index 42ff0f9025..6834ea332e 100644
--- a/extlib/libpng/CMakeLists.txt
+++ b/extlib/libpng/CMakeLists.txt
@@ -65,11 +65,22 @@ option(PNG_HARDWARE_OPTIMIZATIONS "Enable hardware optimizations" ON)
 set(PNG_PREFIX "" CACHE STRING "Prefix to add to the API function names")
 set(DFA_XTRA "" CACHE FILEPATH "File containing extra configuration settings")
 
+# CMake currently sets CMAKE_SYSTEM_PROCESSOR to one of x86_64 or arm64 on macOS,
+# based upon the OS architecture, not the target architecture. As such, we need
+# to check CMAKE_OSX_ARCHITECTURES to identify which hardware-specific flags to
+# enable. Note that this will fail if you attempt to build a universal binary in
+# a single cmake invocation.
+if (APPLE AND CMAKE_OSX_ARCHITECTURES)
+  set(TARGET_ARCH ${CMAKE_OSX_ARCHITECTURES})
+else()
+  set(TARGET_ARCH ${CMAKE_SYSTEM_PROCESSOR})
+endif()
+
 if(PNG_HARDWARE_OPTIMIZATIONS)
 
 # Set definitions and sources for ARM.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" OR
-  CMAKE_SYSTEM_PROCESSOR MATCHES "^aarch64")
+if(TARGET_ARCH MATCHES "^arm" OR
+  TARGET_ARCH MATCHES "^aarch64")
   set(PNG_ARM_NEON_POSSIBLE_VALUES check on off)
   set(PNG_ARM_NEON "check"
       CACHE STRING "Enable ARM NEON optimizations: check|on|off; check is default")
@@ -95,8 +106,8 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" OR
 endif()
 
 # Set definitions and sources for PowerPC.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc*" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "^ppc64*")
+if(TARGET_ARCH MATCHES "^powerpc*" OR
+   TARGET_ARCH MATCHES "^ppc64*")
   set(PNG_POWERPC_VSX_POSSIBLE_VALUES on off)
   set(PNG_POWERPC_VSX "on"
       CACHE STRING "Enable POWERPC VSX optimizations: on|off; on is default")
@@ -118,8 +129,8 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc*" OR
 endif()
 
 # Set definitions and sources for Intel.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^i?86" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "^x86_64*")
+if(TARGET_ARCH MATCHES "^i?86" OR
+   TARGET_ARCH MATCHES "^x86_64*")
   set(PNG_INTEL_SSE_POSSIBLE_VALUES on off)
   set(PNG_INTEL_SSE "on"
       CACHE STRING "Enable INTEL_SSE optimizations: on|off; on is default")
@@ -141,8 +152,8 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^i?86" OR
 endif()
 
 # Set definitions and sources for MIPS.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "mipsel*" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "mips64el*")
+if(TARGET_ARCH MATCHES "mipsel*" OR
+   TARGET_ARCH MATCHES "mips64el*")
   set(PNG_MIPS_MSA_POSSIBLE_VALUES on off)
   set(PNG_MIPS_MSA "on"
       CACHE STRING "Enable MIPS_MSA optimizations: on|off; on is default")
@@ -166,26 +177,26 @@ endif()
 else(PNG_HARDWARE_OPTIMIZATIONS)
 
 # Set definitions and sources for ARM.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "^aarch64")
+if(TARGET_ARCH MATCHES "^arm" OR
+   TARGET_ARCH MATCHES "^aarch64")
   add_definitions(-DPNG_ARM_NEON_OPT=0)
 endif()
 
 # Set definitions and sources for PowerPC.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc*" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "^ppc64*")
+if(TARGET_ARCH MATCHES "^powerpc*" OR
+   TARGET_ARCH MATCHES "^ppc64*")
   add_definitions(-DPNG_POWERPC_VSX_OPT=0)
 endif()
 
 # Set definitions and sources for Intel.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^i?86" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "^x86_64*")
+if(TARGET_ARCH MATCHES "^i?86" OR
+   TARGET_ARCH MATCHES "^x86_64*")
   add_definitions(-DPNG_INTEL_SSE_OPT=0)
 endif()
 
 # Set definitions and sources for MIPS.
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "mipsel*" OR
-   CMAKE_SYSTEM_PROCESSOR MATCHES "mips64el*")
+if(TARGET_ARCH MATCHES "mipsel*" OR
+   TARGET_ARCH MATCHES "mips64el*")
   add_definitions(-DPNG_MIPS_MSA_OPT=0)
 endif()

@@ -412,19 +412,11 @@ else()
                DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/scripts/checksym.awk"
                        "${CMAKE_CURRENT_SOURCE_DIR}/scripts/symbols.def")
 
-  add_custom_target(symbol-check
-                    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.chk")
-
   generate_copy("${CMAKE_CURRENT_BINARY_DIR}/scripts/sym.out"
                 "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym")
   generate_copy("${CMAKE_CURRENT_BINARY_DIR}/scripts/vers.out"
                 "${CMAKE_CURRENT_BINARY_DIR}/libpng.vers")

-  add_custom_target(genvers
-                    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/libpng.vers")
-  add_custom_target(gensym
-                    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym")
-
   add_custom_target("genprebuilt"
                     COMMAND "${CMAKE_COMMAND}"
                             "-DOUTPUT=scripts/pnglibconf.h.prebuilt"