Make folly-related targets comply with verbosity (#6120)

Summary:
Before this fix, `make all` will emit full compilation command when building
object files in the third-party/folly directory even if default verbosity is
0 (AM_DEFAULT_VERBOSITY).

Test Plan (devserver):
```
$make all | tee build.log
$make check
```
Check build.log to verify.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6120

Differential Revision: D18795621

Pulled By: riversand963

fbshipit-source-id: 04641a8359cd4fd55034e6e797ed85de29ee2fe2

Makefile

@@ -2074,6 +2074,9 @@ endif
 .cc.o:
 	$(AM_V_CC)$(CXX) $(CXXFLAGS) -c $< -o $@ $(COVERAGEFLAGS)
 
+.cpp.o:
+	$(AM_V_CC)$(CXX) $(CXXFLAGS) -c $< -o $@ $(COVERAGEFLAGS)
+
 .c.o:
 	$(AM_V_CC)$(CC) $(CFLAGS) -c $< -o $@
 endif
@@ -2082,7 +2085,7 @@ endif
 # ---------------------------------------------------------------------------
 
 all_sources = $(LIB_SOURCES) $(MAIN_SOURCES) $(MOCK_LIB_SOURCES) $(TOOL_LIB_SOURCES) $(BENCH_LIB_SOURCES) $(TEST_LIB_SOURCES) $(ANALYZER_LIB_SOURCES) $(STRESS_LIB_SOURCES)
-DEPFILES = $(all_sources:.cc=.cc.d)
+DEPFILES = $(all_sources:.cc=.cc.d) $(FOLLY_SOURCES:.cpp=.cpp.d)
 
 # Add proper dependency support so changing a .h file forces a .cc file to
 # rebuild.
@@ -2093,6 +2096,10 @@ DEPFILES = $(all_sources:.cc=.cc.d)
 	@$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) \
 	  -MM -MT'$@' -MT'$(<:.cc=.o)' "$<" -o '$@'
 
+%.cpp.d: %.cpp
+	@$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) \
+	  -MM -MT'$@' -MT'$(<:.cpp=.o)' "$<" -o '$@'
+
 ifeq ($(HAVE_POWER8),1)
 DEPFILES_C = $(LIB_SOURCES_C:.c=.c.d)
 DEPFILES_ASM = $(LIB_SOURCES_ASM:.S=.S.d)