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/lib/romlib/Makefile b/lib/romlib/Makefile
index da3d3d5..9ade331 100644
--- a/lib/romlib/Makefile
+++ b/lib/romlib/Makefile
@@ -10,6 +10,7 @@
         toolchains := aarch64
 endif
 
+include ../../make_helpers/common.mk
 include ../../make_helpers/toolchain.mk
 
 ROMLIB_GEN  = ./romlib_generator.py
@@ -29,13 +30,6 @@
         WRAPPER_OBJS = $(WRAPPER_SOURCES:.s=.o)
 endif
 
-V ?= 0
-ifeq ($(V),0)
-  Q := @
-else
-  Q :=
-endif
-
 LDFLAGS := -Wl,--gc-sections -nostdlib
 
 ifeq ($(DEBUG),1)
@@ -53,49 +47,49 @@
 all: $(BUILD_DIR)/romlib.bin $(LIB_DIR)/libwrappers.a
 
 %.o: %.s
-	@echo "  AS      $@"
-	$(Q)$(aarch64-as) -c $(ASFLAGS) -o $@ $<
+	$(s)echo "  AS      $@"
+	$(q)$(aarch64-as) -c $(ASFLAGS) -o $@ $<
 
 $(BUILD_DIR)/%.o: %.s
-	@echo "  AS      $@"
-	$(Q)$(aarch64-as) -c $(ASFLAGS) -o $@ $<
+	$(s)echo "  AS      $@"
+	$(q)$(aarch64-as) -c $(ASFLAGS) -o $@ $<
 
 $(BUILD_DIR)/romlib.ld: romlib.ld.S
-	@echo "  PP      $@"
-	$(Q)$(aarch64-cpp) -E $(PPFLAGS) -o $@ romlib.ld.S
+	$(s)echo "  PP      $@"
+	$(q)$(aarch64-cpp) -E $(PPFLAGS) -o $@ romlib.ld.S
 
 $(BUILD_DIR)/romlib.elf: $(OBJS) $(BUILD_DIR)/romlib.ld
-	@echo "  LD      $@"
-	$(Q)$(aarch64-ld) -T $(BUILD_DIR)/romlib.ld -L$(LIB_DIR) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
+	$(s)echo "  LD      $@"
+	$(q)$(aarch64-ld) -T $(BUILD_DIR)/romlib.ld -L$(LIB_DIR) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
 
 $(BUILD_DIR)/romlib.bin: $(BUILD_DIR)/romlib.elf
-	@echo "  BIN     $@"
-	$(Q)$(aarch64-oc) -O binary $(BUILD_DIR)/romlib.elf $@
+	$(s)echo "  BIN     $@"
+	$(q)$(aarch64-oc) -O binary $(BUILD_DIR)/romlib.elf $@
 
 $(WRAPPER_DIR)/jmpvar.s: $(BUILD_DIR)/romlib.elf
-	@echo "  VAR     $@"
-	$(Q)$(ROMLIB_GEN) genvar --output $@ $<
+	$(s)echo "  VAR     $@"
+	$(q)$(ROMLIB_GEN) genvar --output $@ $<
 
 $(LIB_DIR)/libwrappers.a: $(WRAPPER_DIR)/jmpvar.o $(WRAPPER_OBJS)
-	@echo "  AR      $@"
-	$(Q)$(aarch64-ar) -rc $@ $(WRAPPER_DIR)/jmpvar.o $(WRAPPER_OBJS)
+	$(s)echo "  AR      $@"
+	$(q)$(aarch64-ar) -rc $@ $(WRAPPER_DIR)/jmpvar.o $(WRAPPER_OBJS)
 
 $(BUILD_DIR)/jmptbl.i: ../../$(PLAT_DIR)/jmptbl.i
-	@echo "  PRE     $@"
-	$(Q)$(ROMLIB_GEN) pre --output $@ --deps $(BUILD_DIR)/jmptbl.d $<
+	$(s)echo "  PRE     $@"
+	$(q)$(ROMLIB_GEN) pre --output $@ --deps $(BUILD_DIR)/jmptbl.d $<
 
 $(WRAPPER_SOURCES) &: $(BUILD_DIR)/jmptbl.i
-	@echo "  WRP     $<"
-	$(Q)$(ROMLIB_GEN) genwrappers --bti=$(ENABLE_BTI) -b $(WRAPPER_DIR) $<
+	$(s)echo "  WRP     $<"
+	$(q)$(ROMLIB_GEN) genwrappers --bti=$(ENABLE_BTI) -b $(WRAPPER_DIR) $<
 
 $(WRAPPER_OBJS): $(WRAPPER_DIR)/%.o: $(WRAPPER_DIR)/%.s
 
 $(BUILD_DIR)/jmptbl.s: $(BUILD_DIR)/jmptbl.i
-	@echo "  TBL     $@"
-	$(Q)$(ROMLIB_GEN) gentbl --output $@ --bti=$(ENABLE_BTI) $<
+	$(s)echo "  TBL     $@"
+	$(q)$(ROMLIB_GEN) gentbl --output $@ --bti=$(ENABLE_BTI) $<
 
 clean:
-	@rm -f $(BUILD_DIR)/*
+	$(q)rm -f $(BUILD_DIR)/*
 
 -include $(BUILD_DIR)/romlib.d
 -include $(BUILD_DIR)/jmptbl.d