Use C++14 when compiling CHIP for esp32.

The ESP32 SDK automatically adds -std=-gnu++11 to CXXFLAGS (see
"make/project.mk" in the SDK).  So we just filter it out, and manually
add -std=gnu++14 instead.

config/esp32/components/chip/component.mk

@@ -106,10 +106,11 @@ $(OUTPUT_DIR) :
 fix_cflags = $(filter-out -DHAVE_CONFIG_H,\
                 $(filter-out -D,\
                   $(filter-out IDF_VER%,\
-                    $(sort $(1)) -D$(filter IDF_VER%,$(1))\
-               )))
+                    $(filter-out -std=gnu++11,\
+                      $(sort $(1)) -D$(filter IDF_VER%,$(1))\
+               ))))
 CHIP_CFLAGS = $(call fix_cflags,$(CFLAGS) $(CPPFLAGS))
-CHIP_CXXFLAGS = $(call fix_cflags,$(CXXFLAGS) $(CPPFLAGS))
+CHIP_CXXFLAGS = $(call fix_cflags,$(CXXFLAGS) $(CPPFLAGS)) -std=gnu++14
 
 install-chip : $(OUTPUT_DIR)
 	echo "INSTALL CHIP..."

examples/all-clusters-app/esp32/Makefile

@@ -26,7 +26,7 @@ EXTRA_COMPONENT_DIRS += $(PROJECT_PATH)/third_party/connectedhomeip/config/esp32
                         $(PROJECT_PATH)/../../common/QRCode \
                         $(PROJECT_PATH)/../../common/screen-framework \
 
-CXXFLAGS += -std=c++11 -Os -DLWIP_IPV6_SCOPES=0
+CXXFLAGS += -std=c++14 -Os -DLWIP_IPV6_SCOPES=0
 CPPFLAGS += -Os -DLWIP_IPV6_SCOPES=0 -DCHIP_HAVE_CONFIG_H
 CFLAGS += -Os -DLWIP_IPV6_SCOPES=0
 

examples/temperature-measurement-app/esp32/Makefile

@@ -26,7 +26,7 @@ EXTRA_COMPONENT_DIRS += $(PROJECT_PATH)/third_party/connectedhomeip/config/esp32
                         $(PROJECT_PATH)/../../common/QRCode \
                         $(PROJECT_PATH)/../../common/screen-framework \
 
-CXXFLAGS += -std=c++11 -Os -DLWIP_IPV6_SCOPES=0
+CXXFLAGS += -std=c++14 -Os -DLWIP_IPV6_SCOPES=0
 CPPFLAGS += -Os -DLWIP_IPV6_SCOPES=0 -DCHIP_HAVE_CONFIG_H
 CFLAGS += -Os -DLWIP_IPV6_SCOPES=0