firmware: -nostartfiles -nodefaultlibs are not flags of LD but flags of GCC

It seems that those flags have always been gcc flags, and not ld flags.

After decades of tolerating this, binutils 2.36.x no longer tolerates
those flags but prints an error:

arm-none-eabi-ld: Error: unable to disambiguate: -nostartfiles (did you mean --nostartfiles ?)

See also https://github.com/apache/nuttx/issues/3826 and the related
https://github.com/apache/nuttx/pull/3836 how this was solved in another
project - I adopted that solution here 1:1

Change-Id: Id199e4d03d5aae07a347c98f47791f42c12008c6
---
M src/target/firmware/Makefile.inc
1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/target/firmware/Makefile.inc b/src/target/firmware/Makefile.inc
index 2be240d..86e8f3c 100644
--- a/src/target/firmware/Makefile.inc
+++ b/src/target/firmware/Makefile.inc
@@ -4,7 +4,7 @@
 CROSS_COMPILE?=arm-none-eabi-
 
 CC=gcc
-LD=ld
+LD=gcc
 AR=ar
 SIZE=size
 OBJCOPY=objcopy
@@ -22,7 +22,7 @@
 #ASFLAGS=--g$(DEBUGF) $(INCLUDES) -D__ASSEMBLY__
 ASFLAGS=$(INCLUDES) -D__ASSEMBLY__
 
-LDFLAGS = -nostartfiles -nostdlib -nodefaultlibs --gc-sections --cref
+LDFLAGS = -nostartfiles -nostdlib -nodefaultlibs -Wl,--gc-sections -Wl,--cref
 
 #### QUIET OUTPUT ####
 
@@ -99,8 +99,8 @@
 # define compilation rule, also generates map file
 board/$(2)/$(1).$(3).elf board/$(2)/$(1).$(3).map: $$($(1)_$(2)_$(3)_OBJS) $$($(1)_$(2)_$(3)_LIBS) $$(ENV_$(3)_LDS)
 	$$(Q_LD)$(CROSS_COMPILE)$(LD) $(LDFLAGS) -T $$(ENV_$(3)_LDS) -Bstatic \
-		-Map board/$(2)/$(1).$(3).map -o board/$(2)/$(1).$(3).elf \
-		--start-group $$($(1)_$(2)_$(3)_OBJS) $$($(1)_$(2)_$(3)_LIBS) --end-group
+		-Wl,-Map board/$(2)/$(1).$(3).map -o board/$(2)/$(1).$(3).elf \
+		-Wl,--start-group $$($(1)_$(2)_$(3)_OBJS) $$($(1)_$(2)_$(3)_LIBS) -Wl,--end-group
 
 # define size rule
 board/$(2)/$(1).$(3).size: board/$(2)/$(1).$(3).elf

