build: unify verbosity handling

This change introduces a few helper variables for dealing with verbose
and silent build modes: `silent`, `verbose`, `q` and `s`.

The `silent` and `verbose` variables are boolean values determining
whether the build system has been configured to run silently or
verbosely respectively (i.e. with `--silent` or `V=1`).

These two modes cannot be used together - if `silent` is truthy then
`verbose` is always falsy. As such:

    make --silent V=1

... results in a silent build.

In addition to these boolean variables, we also introduce two new
variables - `s` and `q` - for use in rule recipes to conditionally
suppress the output of commands.

When building silently, `s` expands to a value which disables the
command that follows, and `q` expands to a value which supppresses
echoing of the command:

    $(s)echo 'This command is neither echoed nor executed'
    $(q)echo 'This command is executed but not echoed'

When building verbosely, `s` expands to a value which disables the
command that follows, and `q` expands to nothing:

    $(s)echo 'This command is neither echoed nor executed'
    $(q)echo 'This command is executed and echoed'

In all other cases, both `s` and `q` expand to a value which suppresses
echoing of the command that follows:

    $(s)echo 'This command is executed but not echoed'
    $(q)echo 'This command is executed but not echoed'

The `s` variable is predominantly useful for `echo` commands, where you
always want to suppress echoing of the command itself, whilst `q` is
more useful for all other commands.

Change-Id: I8d8ff6ed714d3cb401946c52955887ed7dca602b
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/tools/cert_create/Makefile b/tools/cert_create/Makefile
index 21523f6..7670939 100644
--- a/tools/cert_create/Makefile
+++ b/tools/cert_create/Makefile
@@ -5,7 +5,6 @@
 #
 
 PLAT		:= none
-V		?= 0
 DEBUG		:= 0
 CRTTOOL		?= cert_create${BIN_EXT}
 BINARY		:= $(notdir ${CRTTOOL})
@@ -16,6 +15,7 @@
 MAKE_HELPERS_DIRECTORY := ../../make_helpers/
 include ${MAKE_HELPERS_DIRECTORY}build_macros.mk
 include ${MAKE_HELPERS_DIRECTORY}build_env.mk
+include ${MAKE_HELPERS_DIRECTORY}common.mk
 include ${MAKE_HELPERS_DIRECTORY}defaults.mk
 include ${MAKE_HELPERS_DIRECTORY}toolchain.mk
 
@@ -60,12 +60,6 @@
   HOSTCCFLAGS += -O2 -DLOG_LEVEL=20
 endif
 
-ifeq (${V},0)
-  Q := @
-else
-  Q :=
-endif
-
 HOSTCCFLAGS += ${DEFINES}
 # USING_OPENSSL3 flag will be added to the HOSTCCFLAGS variable with the proper
 # computed value.
@@ -89,19 +83,19 @@
 all: --openssl ${BINARY}
 
 ${BINARY}: ${OBJECTS} Makefile
-	@echo "  HOSTLD  $@"
-	@echo 'const char build_msg[] = "Built : "__TIME__", "__DATE__; \
+	$(s)echo "  HOSTLD  $@"
+	$(q)echo 'const char build_msg[] = "Built : "__TIME__", "__DATE__; \
                 const char platform_msg[] = "${PLAT_MSG}";' | \
                 $(host-cc) -c ${HOSTCCFLAGS} -xc - -o src/build_msg.o
-	${Q}$(host-cc) src/build_msg.o ${OBJECTS} ${LIB_DIR} ${LIB} -o $@
+	$(q)$(host-cc) src/build_msg.o ${OBJECTS} ${LIB_DIR} ${LIB} -o $@
 
 %.o: %.c
-	@echo "  HOSTCC  $<"
-	${Q}$(host-cc) -c ${HOSTCCFLAGS} ${INC_DIR} $< -o $@
+	$(s)echo "  HOSTCC  $<"
+	$(q)$(host-cc) -c ${HOSTCCFLAGS} ${INC_DIR} $< -o $@
 
 --openssl:
 ifeq ($(DEBUG),1)
-	@echo "Selected OpenSSL version: ${OPENSSL_CURRENT_VER}"
+	$(s)echo "Selected OpenSSL version: ${OPENSSL_CURRENT_VER}"
 endif
 
 clean: