[Bug preprocessor/94657] New: [patch] libcpp uses 'AR = ar' tool even if --build/--host are passed explicitly.

[slyfox at inbox dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94657

            Bug ID: 94657
           Summary: [patch] libcpp uses 'AR = ar' tool even if
                    --build/--host are passed explicitly.
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at inbox dot ru
  Target Milestone: ---

Created attachment 48305
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48305&action=edit
libcpp-ar.patch

Initially reported by Agostino Sarubbo as https://bugs.gentoo.org/718004.

There Gentoo builds gcc-9.3.0 as:
    --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu
and observes 'ar' being called by libcpp. It should be 'x86_64-pc-linux-gnu-ar'
instead.

libcpp/Makefile.in hardcodes 'AR = ar' (but does not hardcode RANLIB for
example:  'RANLIB = @RANLIB@'). 

A few other tools do it:

  $ git grep 'AR = ar' | cat
  gcc/ada/gcc-interface/Makefile.in:AR = ar
  intl/Makefile.in:AR = ar
  libcpp/Makefile.in:AR = ar
  libdecnumber/Makefile.in:AR = ar

but only libcpp refers 'ar' and fails build when 'ar' does not exist:

  ar cru libcpp.a charset.o directives.o directives-only.o errors.o expr.o
files.o identifiers.o init.o lex.o line-map.o macro.o mkdeps.o pch.o symtab.o
traditional.o
  /bin/bash: ar: command not found

Attached patch adds AR detection similar to other libraries.

But maybe it should be set in top-level Makefile?