mk: Cross-eyed hacks to support cross-libtool.

For a long time, when cross-building, say from native=amd64 to
target=powerpc, it was necessary to:

1. cross-build a _powerpc_ package called cross-libtool-base-powerpc,
   and then

2. install the powerpc package _natively_ with `pkg_add -m x86_64' to
   override the architecture check that normally forbids this kind of
   shenanigans,

in order to cross-build anything that uses libtool as a tool.

This is partly because libtool doesn't follow the normal GNU
convention of `./configure --build=<native platform> --host=<platform
package will run on> --target=<platform package is configured to
operate on>' -- in this example, build=amd64, host=amd64,
target=powerpc.

Instead, libtool expects to be cross-built itself, even if it's going
to run as a tool.  It's not as bonkers as it sounds at first: libtool
is just a shell script, and it caches various information about the
(cross-building!) toolchain it is built with so it can use that
information later when it is run as a tool itself to cross-compile
other software.

To make this work, we need to create the toolchain wrappers for
libtool _as if_ we were cross-building even if we are building a
native package.  So mk/tools uses a new flag TOOLS_USE_CROSS_COMPILE
instead of USE_CROSS_COMPILE, and libtool internally sets
MACHINE_ARCH=${TARGET_ARCH} (in the example above, powerpc) to make
it look like we're cross-building.  The new TOOLS_CROSS_DESTDIR is an
alias for the (defaulted) CROSS_DESTDIR, which must now be set
unconditionally in mk.conf in order for libtool to know where the
cross-destdir will be; _CROSS_DESTDIR remains empty when building any
native packages (including the native cross-libtool package).

Finally, we need to make the resulting package be a native package,
with MACHINE_ARCH set to the one that it will be installed on (in the
example above, amd64), so I added an indirection _BUILD_DEFS.${var}
to replace var on its own in the build definitions that get baked
into the package, shown by `pkg_info -B'.  Setting
_BUILD_DEFS.MACHINE_ARCH=${NATIVE_MACHINE_ARCH} ensures that this
mutant hybrid cross-built libtool still produces a native package.

All of this logic is gated on setting USE_CROSS_COMPILE in mk.conf or
LIBTOOL_CROSS_COMPILE in the package makefile, so it should be safe
for non-cross-builds -- when USE_CROSS_COMPILE=no and you're not
building cross-libtool, everything is as before.

1 files changed, 4 insertions, 4 deletions

diff --git a/mk/wrapper/bsd.wrapper.mk b/mk/wrapper/bsd.wrapper.mk
index 9d9cf40d076..fe06414a204 100644
--- a/mk/wrapper/bsd.wrapper.mk
+++ b/mk/wrapper/bsd.wrapper.mk
@@ -1,4 +1,4 @@
-# $NetBSD: bsd.wrapper.mk,v 1.104 2022/03/13 06:26:57 nia Exp $
+# $NetBSD: bsd.wrapper.mk,v 1.105 2022/04/04 11:23:07 riastradh Exp $
 #
 # Copyright (c) 2005 The NetBSD Foundation, Inc.
 # All rights reserved.
@@ -363,7 +363,7 @@ _WRAP_CMD_SINK.CXX=	${_WRAP_CMD_SINK.CC}
 _WRAP_CMD_SINK.LD=	${WRAPPER_TMPDIR}/cmd-sink-irix-ld
 .endif
 
-.if !empty(USE_CROSS_COMPILE:M[yY][eE][sS])
+.if !empty(TOOLS_USE_CROSS_COMPILE:M[yY][eE][sS])
 _WRAP_CMD_SINK.CC=	${WRAPPER_TMPDIR}/cmd-sink-cross-gcc
 _WRAP_CMD_SINK.CPP=	${WRAPPER_TMPDIR}/cmd-sink-cross-cpp
 _WRAP_CMD_SINK.CXX=	${WRAPPER_TMPDIR}/cmd-sink-cross-gxx
@@ -540,9 +540,9 @@ ${WRAPPER_TMPDIR}/${w}: ${WRAPPER_SRCDIR}/${w}
 	${RUN} ${CAT} ${.ALLSRC} | ${_WRAP_SH_CRUNCH_FILTER} > ${.TARGET}
 .endfor
 
-.if !empty(USE_CROSS_COMPILE:M[yY][eE][sS])
+.if !empty(TOOLS_USE_CROSS_COMPILE:M[yY][eE][sS])
 _WRAP_CROSS_GCC_FILTER+= ${SED}						\
-	-e "s|@CROSS_DESTDIR@|${_CROSS_DESTDIR:Q}|g"			\
+	-e "s|@CROSS_DESTDIR@|${TOOLS_CROSS_DESTDIR:Q}|g"		\
 	-e "s|@PREFIX@|${PREFIX:Q}|g"
 ${WRAPPER_TMPDIR}/cmd-sink-cross-gcc: ${WRAPPER_SRCDIR}/cmd-sink-cross-gcc
 	${RUN} ${MKDIR} ${.TARGET:H}