demos: tidy up makefiles, fix warnings

Update makefiles so that consistent patterns are used.  Object files
are compiled from source using an implicit rule (but using our
CFLAGS); for linking, we give an explicit rule.  Ensure that "make
test" works in each subdirectory (even if it does not actually run any
applications).  The top-level demo makefile now works.

The makefiles are not make-agnostic.  e.g. they use the variable $(RM)
in "clean" recipes, which is defined in gnu-make but may not be
defined in others.

Part of #17806

Testing:

  $ cd demo
  $ make test

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22698)

1 files changed, 14 insertions, 4 deletions

diff --git a/demos/cms/Makefile b/demos/cms/Makefile
index 7c8f30d632..3d4cb90750 100644
--- a/demos/cms/Makefile
+++ b/demos/cms/Makefile
@@ -15,18 +15,28 @@ TESTS = cms_comp \
         cms_uncomp \
         cms_ver
 
-CFLAGS  = -I../../include -g
+CFLAGS  = -I../../include -g -Wall
 LDFLAGS = -L../..
 LDLIBS  = -lcrypto
 
 all: $(TESTS)
 
+cms_comp: cms_comp.o
+cms_ddec: cms_ddec.o
+cms_dec: cms_dec.o
+cms_denc: cms_denc.o
+cms_enc: cms_enc.o
+cms_sign: cms_sign.o
+cms_sign2: cms_sign2.o
+cms_uncomp: cms_uncomp.o
+cms_ver: cms_ver.o
+
+$(TESTS):
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $< $(LDLIBS)
+
 clean:
 	$(RM) $(TESTS) *.o
 
-cms_%: cms_%.c
-	$(CC) $(CFLAGS) $(LDFLAGS) -o "$@" "$<" $(LDLIBS)
-
 test: all
 	@echo "\nCMS tests:"
 	LD_LIBRARY_PATH=../.. ./cms_enc