chore: revert "fix LEAN_PATH for building stage2+ Leanc.lean" (#8692)

Reverts #8685 pending Windows fix

Author: Kha

src/stdlib.make.in

@@ -62,7 +62,7 @@ Lean: Std
 
 Leanc: Lean
 ifneq "${STAGE}" "0"
-	+"${LEAN_BIN}/leanmake" -C "${CMAKE_BINARY_DIR}/leanc" lib PKG=Leanc $(LEANMAKE_OPTS) OUT="${CMAKE_LIBRARY_OUTPUT_DIRECTORY}" LIB_OUT="${CMAKE_LIBRARY_OUTPUT_DIRECTORY}" OLEAN_OUT="${CMAKE_LIBRARY_OUTPUT_DIRECTORY}"
+	+"${LEAN_BIN}/leanmake" -C "${CMAKE_BINARY_DIR}/leanc" lib PKG=Leanc $(LEANMAKE_OPTS) OUT="${CMAKE_LIBRARY_OUTPUT_DIRECTORY}" LIB_OUT="${CMAKE_LIBRARY_OUTPUT_DIRECTORY}"
 endif
 
 Lake: