How should b2's custom behavior access the toolchain

[situNagisa]

I am trying to build xv6 using b2. I build from bootblock. The xv6 makefile is as follows::

bootblock: bootasm.S bootmain.c
	$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
	$(OBJDUMP) -S bootblock.o > bootblock.asm
	$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
	./sign.pl bootblock

And the jam I can write is as follows

project xv6 : ;

obj bootmain 
	: bootmain.c 
	: 	<link>static 
		<include>. 
		<debug-symbols>on 
		<rtti>off 
		<exception-handling>off
		<extern-c-nothrow>on
		<address-model>32
		<cflags>-O2
		<cflags>-fno-builtin
		<cflags>-fno-strict-aliasing
		<cflags>-fno-omit-frame-pointer
		<cflags>-fno-pic
		<cflags>-fno-pie
		<cflags>-no-pie
		<cflags>-nostdinc
		<cflags>-MD
		<cflags>-ggdb 
	;
obj bootasm 
	: bootasm.S 
	: 	<link>static 
		<include>. 
		<debug-symbols>on 
		<rtti>off 
		<exception-handling>off
		<extern-c-nothrow>on
		<address-model>32
		<cflags>-O2
		<cflags>-fno-builtin
		<cflags>-fno-strict-aliasing
		<cflags>-fno-omit-frame-pointer
		<cflags>-fno-pic
		<cflags>-fno-pie
		<cflags>-no-pie
		<cflags>-nostdinc
		<cflags>-MD
		<cflags>-ggdb 
	;

I got stuck on how to link bootmain and bootasm. I tried to write:

make bootblock 
	: bootmain bootasm 
	:	@make_bootblock
	;
actions make_bootblock
{
	$(LD) -m elf_i386 -N -e start -Ttext 0x7C00 -o $(<) $(>)
	# $(.LD) -m elf_i386 -N -e start -Ttext 0x7C00 -o $(<) $(>)
} 

But LD can't be found (it's empty), as I tried again

exe bootblock-elf
	: bootmain bootasm 
	: 	<linkflags>-Wl,-melf_i386
		<linkflags>-Wl,-N
		<linkflags>-Wl,-estart
		<linkflags>-Wl,-Ttext=0x7c00
	;

This will give us an error:

warning: No toolsets are configured.
warning: Configuring default toolset "gcc".
warning: If the default is wrong, your build may not work correctly.
warning: Use the "toolset=xxxxx" option to override our guess.
warning: For more configuration options, please consult
warning: https://www.bfgroup.xyz/b2/manual/release/index.html#bbv2.overview.configuration
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../../lib/libstdc++.a when searching for -lstdc++
/usr/sbin/ld: skipping incompatible /lib/../lib/libstdc++.a when searching for -lstdc++
/usr/sbin/ld: skipping incompatible /usr/lib/../lib/libstdc++.a when searching for -lstdc++
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../libstdc++.a when searching for -lstdc++
/usr/sbin/ld: skipping incompatible /usr/lib/libstdc++.a when searching for -lstdc++
/usr/sbin/ld: cannot find -lstdc++: No such file or directory
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../../lib/libm.a when searching for -lm
/usr/sbin/ld: skipping incompatible /lib/../lib/libm.a when searching for -lm
/usr/sbin/ld: skipping incompatible /usr/lib/../lib/libm.a when searching for -lm
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../libm.a when searching for -lm
/usr/sbin/ld: skipping incompatible /usr/lib/libm.a when searching for -lm
/usr/sbin/ld: cannot find -lm: No such file or directory
/usr/sbin/ld: cannot find -lgcc_s: No such file or directory
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/libgcc.a when searching for -lgcc
/usr/sbin/ld: cannot find -lgcc: No such file or directory
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../../lib/libc.a when searching for -lc
/usr/sbin/ld: skipping incompatible /lib/../lib/libc.a when searching for -lc
/usr/sbin/ld: skipping incompatible /usr/lib/../lib/libc.a when searching for -lc
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/../../../libc.a when searching for -lc
/usr/sbin/ld: skipping incompatible /usr/lib/libc.a when searching for -lc
/usr/sbin/ld: cannot find -lc: No such file or directory
/usr/sbin/ld: cannot find -lgcc_s: No such file or directory
/usr/sbin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/libgcc.a when searching for -lgcc
/usr/sbin/ld: cannot find -lgcc: No such file or directory
collect2: error: ld returned 1 exit status

Obviously, he compiled it as a c++ program, how can I link it correctly and get the bootblock using objcopy