Provide <triplet>-<tool> wrappers and links to many llvm tools

Provide wrappers named <triplet>-gcc and <triplet>-g++ as well,
to ease cross compilation with e.g. autotools, to allow just
specifying --host=<triplet>.

Provide wrappers for objdump and ld that provide specific output
that autotools look for.

Provide <triplet>-strip as a symlink to /bin/true, since there is
no strip tool available yet (and llvm-objcopy doesn't support
COFF yet).

wrappers/ld-wrapper.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+if [ "$1" = "--help" ]; then
+	cat<<EOF
+GNU ld impersonation
+We don't support --enable-auto-import, but libtool may look for this flag.
+EOF
+	exit 0
+fi
+if [ "$1" = "-v" ]; then
+	# This isn't implemented in the lld mingw frontend, so don't
+	# pass the -m <machine> option in this case.
+	ld.lld -v
+	exit 0
+fi
+
+TARGET="$(basename $0 | sed 's/-[^-]*$//')"
+ARCH=$(echo $TARGET | sed 's/-.*//')
+case $ARCH in
+i686)    M=i386pe   ;;
+x86_64)  M=i386pep  ;;
+armv7)   M=thumb2pe ;;
+aarch64) M=arm64pe  ;;
+esac
+ld.lld -m $M "$@"