When the buildkernel stage 2.3 (build tools) runs, the PATH is still set

to the default from the top-level Makefile.  Therefore, invocations of
lex and yacc (used during building of aicasm) will use the executables
in /usr/bin, not those optionally built during the previous buildworld
or kernel-toolchain.  This makes kernel builds from older FreeBSD
releases more difficult than necessary.

Fix this by setting PATH to ${BPATH}:${PATH} in stage 2.3, so the
bootstrap tools directories are searched before the regular ones.

Silence from:	svn-src-{all,head}
MFC after:	1 week

Makefile.inc1

@@ -832,6 +832,7 @@ buildkernel:
 	@echo ">>> stage 2.3: build tools"
 	@echo "--------------------------------------------------------------"
 	cd ${KRNLOBJDIR}/${_kernel}; \
+	    PATH=${BPATH}:${PATH} \
 	    MAKESRCPATH=${KERNSRCDIR}/dev/aic7xxx/aicasm \
 	    ${MAKE} SSP_CFLAGS= -DNO_CPU_CFLAGS -DNO_CTF \
 	    -f ${KERNSRCDIR}/dev/aic7xxx/aicasm/Makefile
@@ -839,6 +840,7 @@ buildkernel:
 .if !defined(MODULES_WITH_WORLD) && !defined(NO_MODULES) && exists(${KERNSRCDIR}/modules)
 .for target in obj depend all
 	cd ${KERNSRCDIR}/modules/aic7xxx/aicasm; \
+	    PATH=${BPATH}:${PATH} \
 	    MAKEOBJDIRPREFIX=${KRNLOBJDIR}/${_kernel}/modules \
 	    ${MAKE} SSP_CFLAGS= -DNO_CPU_CFLAGS -DNO_CTF ${target}
 .endfor