GNUmakefile: fix installation logic for libstdbuf

It is better to check whether we're actually compiling libstdbuf, rather than to check whether
we're on windows, in order to decide whether libstdbuf should get installed.

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>

.github/workflows/CICD.yml

@@ -379,6 +379,11 @@ jobs:
         set -x
         # Regression-test for https://github.com/uutils/coreutils/issues/8701
         make UTILS="rm chmod chown chgrp mv du"
+        # Verifies that
+        # 1. there is no "error: none of the selected packages contains this
+        # feature: feat_external_libstdbuf"
+        # 2. the makefile doesn't try to install libstdbuf even though stdbuf is skipped
+        DESTDIR=/tmp/ make SKIP_UTILS="stdbuf" install
 
   build_rust_stable:
     name: Build/stable

GNUmakefile

@@ -482,7 +482,7 @@ endif
 
 install: build install-manpages install-completions install-locales
 	mkdir -p $(INSTALLDIR_BIN)
-ifneq ($(OS),Windows_NT)
+ifneq (,$(and $(findstring stdbuf,$(UTILS)),$(findstring feat_external_libstdbuf,$(CARGOFLAGS))))
 	mkdir -p $(DESTDIR)$(LIBSTDBUF_DIR)
 	$(INSTALL) -m 755 $(BUILDDIR)/deps/libstdbuf* $(DESTDIR)$(LIBSTDBUF_DIR)/
 endif