Revert "Reviewed Makefile clean target to use CMD shell on Windows"

This reverts commit ab47c6401e.

src/Makefile

@@ -36,6 +36,7 @@
 
 # NOTE: Highly recommended to read the raylib Wiki to know how to compile raylib for different platforms
 # https://github.com/raysan5/raylib/wiki
+
 .PHONY: all clean install uninstall
 
 # Define required environment variables
@@ -105,7 +106,6 @@ ROOT = $(shell whoami)
 
 # By default we suppose we are working on Windows
 HOST_PLATFORM_OS ?= WINDOWS
-PLATFORM_OS ?= WINDOWS
 
 # Determine PLATFORM_OS in case PLATFORM_DESKTOP selected
 ifeq ($(PLATFORM),PLATFORM_DESKTOP)
@@ -148,12 +148,6 @@ ifeq ($(PLATFORM),PLATFORM_DRM)
     endif
 endif
 
-ifeq ($(PLATFORM_OS),WINDOWS)
-    # Make uses by default Sh shell, if a different shell is required, it must be specified
-    # On Windows we set CMD as default shell to allow calling del command on clean target
-    SHELL := cmd
-endif
-
 ifeq ($(PLATFORM),PLATFORM_WEB)
     # Emscripten required variables
     EMSDK_PATH         ?= C:/emsdk
@@ -737,6 +731,12 @@ endif
 # Clean everything
 clean:
 ifeq ($(PLATFORM_OS),WINDOWS)
+	# Make always tries to run build rules under sh.exe by default
+	# So if sh.exe is present in the PATH on windows, the del commands will fail
+	# see README.W32 of GNU Make for more details
+	# It is not specified earlier in the Makefile, because then cross-compilation
+	# will also fail.
+	SHELL = cmd
 	del *.o /s
 	cd $(RAYLIB_RELEASE_PATH)
 	del lib$(RAYLIB_LIB_NAME).a /s