Try to source in a difference way

Author: mcbarton

docs/conf.py

@@ -56,7 +56,7 @@
 command_emscripten = 'git clone https://github.com/emscripten-core/emsdk.git {0}/emsdk;\
                 {0}/emsdk/emsdk install  3.1.73;\
                 {0}/emsdk/emsdk activate 3.1.73;\
-                source {0}/emsdk/emsdk_env.sh;\
+                . {0}/emsdk/emsdk_env.sh;\
                 export SYSROOT_PATH={0}/emsdk/upstream/emscripten/cache/sysroot;\
                 git clone --depth=1 --branch release/20.x https://github.com/llvm/llvm-project.git {0}/llvm-project;\
                 cd {0}/llvm-project;\