Fix cpu.ppc for strict vocabulary search path semantics

basis/cpu/ppc/bootstrap.factor

@@ -4,6 +4,7 @@ USING: bootstrap.image.private kernel kernel.private namespaces
 system cpu.ppc.assembler compiler.codegen.fixup compiler.units
 compiler.constants math math.private layouts words
 vocabs slots.private locals.backend ;
+FROM: cpu.ppc.assembler => B ;
 IN: bootstrap.ppc
 
 4 \ cell set

basis/cpu/ppc/ppc.factor

@@ -7,6 +7,7 @@ cpu.ppc.assembler cpu.ppc.assembler.backend literals compiler.cfg.registers
 compiler.cfg.instructions compiler.constants compiler.codegen
 compiler.codegen.fixup compiler.cfg.intrinsics
 compiler.cfg.stack-frame compiler.units ;
+FROM: cpu.ppc.assembler => B ;
 IN: cpu.ppc
 
 ! PowerPC register assignments: