Fix Makefile emscripten path (#2785)

src/Makefile

@@ -181,13 +181,15 @@ ifeq ($(PLATFORM),PLATFORM_WEB)
 endif
 
 ifeq ($(PLATFORM),PLATFORM_WEB)
-    # Emscripten required variables
-    EMSDK_PATH         ?= C:/emsdk
-    EMSCRIPTEN_PATH    ?= $(EMSDK_PATH)/upstream/emscripten
-    CLANG_PATH          = $(EMSDK_PATH)/upstream/bin
-    PYTHON_PATH         = $(EMSDK_PATH)/python/3.9.2-1_64bit
-    NODE_PATH           = $(EMSDK_PATH)/node/14.15.5_64bit/bin
-    export PATH         := $(EMSDK_PATH):$(EMSCRIPTEN_PATH):$(CLANG_PATH):$(NODE_PATH):$(PYTHON_PATH):C:\raylib\MinGW\bin:$(PATH)
+    ifeq ($(PLATFORM_OS), WINDOWS)
+        # Emscripten required variables
+        EMSDK_PATH         ?= C:/emsdk
+        EMSCRIPTEN_PATH    ?= $(EMSDK_PATH)/upstream/emscripten
+        CLANG_PATH         := $(EMSDK_PATH)/upstream/bin
+        PYTHON_PATH        := $(EMSDK_PATH)/python/3.9.2-1_64bit
+        NODE_PATH          := $(EMSDK_PATH)/node/14.15.5_64bit/bin
+        export PATH        := $(EMSDK_PATH);$(EMSCRIPTEN_PATH);$(CLANG_PATH);$(NODE_PATH);$(PYTHON_PATH);C:/raylib/MinGW/bin;$(PATH)
+    endif
 endif
 
 ifeq ($(PLATFORM),PLATFORM_ANDROID)