From 6842c58adc2c882242a39b46fc45c50b32e1921f Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@qt.io>
Date: Fri, 30 Aug 2019 10:07:09 +0200
Subject: [PATCH] Fix CMake build with Emscripten

When building with Emscripten, linkage to libm is neither required
nor working. As find_library will fail, M_LIBRARY will be set to
NOTFOUND and the build would fail later. The build works just fine
without libm linkage.
---
 CMakeLists.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c85aa74cf..013f76e9f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,7 @@
 # Revised by Kyle Bentley, 2018
 # Revised by David Callu, 2020
 # Revised by Steve Robinson, 2020
+# Revised by Simon Hausmann, 2020
 
 # This code is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
@@ -45,7 +46,7 @@ if(NOT PNG_BUILD_ZLIB)
   include_directories(${ZLIB_INCLUDE_DIRS})
 endif()
 
-if(UNIX AND NOT APPLE AND NOT BEOS AND NOT HAIKU)
+if(UNIX AND NOT APPLE AND NOT BEOS AND NOT HAIKU AND NOT EMSCRIPTEN)
   find_library(M_LIBRARY m)
 else()
   # libm is not needed and/or not available