debug/ltrace: Fix HOST_OS and ar

HOST_OS really is the target OS. Allow setting it for configure
via an environment variable.
libltrace.a should have an index:
Allow ar to be set as an environment variable, and generate
an index in this lib.

Reported-by: "Guylhem Aznar" <crossgcc@guylhem.net>
Signed-off-by: "Titus von Boxberg" <titus@v9g.de>
(transplanted from f86af11138ea2b2ecd4876d9c6c24f58ba4d68ac)

--- binutils/libiberty/Makefile.in.mps	2004-05-13 15:53:17.000000000 +0200

+++ binutils/libiberty/Makefile.in	2004-05-13 15:52:53.000000000 +0200

@@ -224,6 +224,7 @@ $(TARGETLIB): $(REQUIRED_OFILES) $(EXTRA

 	  $(AR) $(AR_FLAGS) $(TARGETLIB) \

 	    $(REQUIRED_OFILES) $(EXTRA_OFILES) $(LIBOBJS); \

 	  $(RANLIB) $(TARGETLIB); \

+	  cp $(TARGETLIB) ../ ; \

 	  cd ..; \

 	else true; fi