as suggested by Oliver:

- only output messages if MAKELEVEL is 0
- indent nested ifeq
- use if (,) syntax

samples/Makefile

@@ -344,7 +344,9 @@ samples: $(EXELIST_$(SYS))
 
 # empty target used to skip systems that will not work with any program in this dir
 notavailable:
-	@echo "warning: generic samples not available for" $(SYS)
+ifeq ($(MAKELEVEL),0)
+	@echo "info: generic samples not available for" $(SYS)
+endif
 
 disk: $(DISK_$(SYS))
 

samples/geos/Makefile

@@ -5,13 +5,15 @@ SYS ?= geos-cbm
 
 # If SYS was given on the commandline, redirect "c64" to "geos-cbm" and
 # "apple2enh" to "geos-apple"
-ifeq "$(origin SYS)" "command line"
-ifeq "$(SYS)" "c64"
-  override SYS = geos-cbm
-endif
-ifeq "$(SYS)" "apple2enh"
-  override SYS = geos-apple
-endif
+ifeq ($(origin SYS),command line)
+  ifeq ($(SYS),c64)
+    override SYS = geos-cbm
+    $(info GEOS: c64 -> geos-cbm)
+  endif
+  ifeq ($(SYS),apple2enh)
+    override SYS = geos-apple
+    $(info GEOS: apple2enh -> geos-apple)
+  endif
 endif
 
 # Just the usual way to find out if we're
@@ -80,7 +82,9 @@ samples: $(EXELIST_$(SYS))
 	$(foreach dir,$(DIRLIST),$(SUBDIR_recipe))
 else
 samples:
-	@echo "warning: geos samples not available for" $(SYS)
+  ifeq ($(MAKELEVEL),0)
+	@echo "info: geos samples not available for" $(SYS)
+  endif
 endif
 
 	

samples/geos/grc/Makefile

@@ -41,7 +41,9 @@ ifneq ($(EXELIST_$(SYS)),)
 samples: $(EXELIST_$(SYS))
 else
 samples:
-	@echo "warning: grc sample not available for" $(SYS)
+  ifeq ($(MAKELEVEL),0)
+	@echo "info: grc sample not available for" $(SYS)
+  endif
 endif
 
 test.s: test.grc

samples/tutorial/Makefile

@@ -81,6 +81,9 @@ hello: hello.c text.s
 
 # empty target used to skip systems that will not work with any program in this dir
 notavailable:
-	@echo "warning: tutorial sample not available for" $(SYS)
+ifeq ($(MAKELEVEL),0)
+	@echo "info: tutorial sample not available for" $(SYS)
+endif
+
 clean:
 	@$(DEL) hello 2>$(NULLDEV)