build: Change -isystem= to -isystem

This is better for ide parsing

Signed-off-by: Huaqi Fang <[email protected]>

Build/toolchain/nuclei_gnu.mk

@@ -42,17 +42,17 @@ LDLIBS += -lc -lgcc
 else ifeq ($(STDCLIB),newlib_fast)
 LDLIBS += -lc_nano -lgcc
 STDCLIB_LDFLAGS += -u _printf_float -u _scanf_float
-COMMON_FLAGS += -isystem=/include/newlib-nano
+COMMON_FLAGS += -isystem /include/newlib-nano
 else ifeq ($(STDCLIB),newlib_small)
 LDLIBS += -lc_nano -lgcc
 STDCLIB_LDFLAGS += -u _printf_float
-COMMON_FLAGS += -isystem=/include/newlib-nano
+COMMON_FLAGS += -isystem /include/newlib-nano
 else ifeq ($(STDCLIB),newlib_nano)
 LDLIBS += -lc_nano -lgcc
-COMMON_FLAGS += -isystem=/include/newlib-nano
+COMMON_FLAGS += -isystem /include/newlib-nano
 else
 LDLIBS += -lc_nano -lgcc
-COMMON_FLAGS += -isystem=/include/newlib-nano
+COMMON_FLAGS += -isystem /include/newlib-nano
 endif
 ###
 else ifneq ($(findstring libncrt,$(STDCLIB)),)
@@ -63,7 +63,7 @@ ifeq ($(COMPILE_PREFIX),riscv64-unknown-elf-)
 LDLIBS += -lheapops_$(NCRTHEAP)
 endif
 endif
-COMMON_FLAGS += -isystem=/include/libncrt
+COMMON_FLAGS += -isystem /include/libncrt
 ###
 else ifeq ($(STDCLIB),nostd)
 ### Handle cases when no standard system directories for header files