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/nxp/create_pbl/pbl_ch2.mk b/tools/nxp/create_pbl/pbl_ch2.mk
index e6f1d8b..bf05a12 100644
--- a/tools/nxp/create_pbl/pbl_ch2.mk
+++ b/tools/nxp/create_pbl/pbl_ch2.mk
@@ -15,12 +15,12 @@
 ifeq ($(SECURE_BOOT),yes)
 pbl: ${BUILD_PLAT}/bl2.bin
 ifeq ($(RCW),"")
-	${Q}echo "Platform ${PLAT} requires rcw file. Please set RCW to point to the right RCW file for boot mode ${BOOT_MODE}"
+	$(s)echo "Platform ${PLAT} requires rcw file. Please set RCW to point to the right RCW file for boot mode ${BOOT_MODE}"
 else
 	# Generate header for bl2.bin
-	$(Q)$(CST_DIR)/create_hdr_isbc --in ${BUILD_PLAT}/bl2.bin --out ${BUILD_PLAT}/hdr_bl2 ${BL2_INPUT_FILE}
+	$(q)$(CST_DIR)/create_hdr_isbc --in ${BUILD_PLAT}/bl2.bin --out ${BUILD_PLAT}/hdr_bl2 ${BL2_INPUT_FILE}
 	# Compile create_pbl tool
-	${Q}${MAKE} CPPFLAGS="-DVERSION='\"${VERSION_STRING}\"'" --no-print-directory -C ${CREATE_PBL_TOOL_PATH};\
+	$(q)${MAKE} CPPFLAGS="-DVERSION='\"${VERSION_STRING}\"'" --no-print-directory -C ${CREATE_PBL_TOOL_PATH};\
 	# Add bl2.bin to RCW
 	${CREATE_PBL} -r ${RCW} -i ${BUILD_PLAT}/bl2.bin -b ${BOOT_MODE} -c ${SOC_NUM} -d ${BL2_BASE} -e ${BL2_BASE}\
 			-o ${BUILD_PLAT}/bl2_${BOOT_MODE}.pbl ;\
@@ -31,7 +31,7 @@
 # Swapping of RCW is required for QSPi Chassis 2 devices
 ifeq (${BOOT_MODE}, qspi)
 ifeq ($(SWAP),1)
-	${Q}echo "Byteswapping RCW for QSPI"
+	$(s)echo "Byteswapping RCW for QSPI"
 	${BYTE_SWAP} ${BUILD_PLAT}/bl2_${BOOT_MODE}_sec.pbl;
 endif # SWAP
 endif # BOOT_MODE
@@ -39,22 +39,19 @@
 endif
 else  # NON SECURE_BOOT
 ifeq ($(RCW),"")
-	${Q}echo "Platform ${PLAT} requires rcw file. Please set RCW to point to the right RCW file for boot mode ${BOOT_MODE}"
+	$(s)echo "Platform ${PLAT} requires rcw file. Please set RCW to point to the right RCW file for boot mode ${BOOT_MODE}"
 else
 	# -a option appends the image for Chassis 3 devices in case of non secure boot
-	${Q}${MAKE} CPPFLAGS="-DVERSION='\"${VERSION_STRING}\"'" --no-print-directory -C ${CREATE_PBL_TOOL_PATH};
+	$(q)${MAKE} CPPFLAGS="-DVERSION='\"${VERSION_STRING}\"'" --no-print-directory -C ${CREATE_PBL_TOOL_PATH};
 	${CREATE_PBL} -r ${RCW} -i ${BUILD_PLAT}/bl2.bin -b ${BOOT_MODE} -c ${SOC_NUM} -d ${BL2_BASE} -e ${BL2_BASE} \
 	-o ${BUILD_PLAT}/bl2_${BOOT_MODE}.pbl ;
 # Swapping of RCW is required for QSPi Chassis 2 devices
 ifeq (${BOOT_MODE}, qspi)
 ifeq ($(SWAP),1)
-	${Q}echo "Byteswapping RCW for QSPI"
+	$(s)echo "Byteswapping RCW for QSPI"
 	${BYTE_SWAP} ${BUILD_PLAT}/bl2_${BOOT_MODE}.pbl;
 endif # SWAP
 endif # BOOT_MODE
 	cd ${CREATE_PBL_TOOL_PATH}; ${MAKE} clean ; cd -;
 endif
 endif # SECURE_BOOT
-
-
-