Experimental new redoconf C/C++ build/autoconfiguration system.

To test it out, try this:
	./do -j10 build
	cd docs/cookbook/c
	redo -j10 test

It should detect all the compilers on your system and make three
separate builds for each one: normal, debug, and optimized.  Then it
tries to run a test program under each one.

If there are windows cross compilers and you also have 'wine'
installed, it'll try running the test program under wine as well.

redoconf currently has no documentation other than the example program.
We'll fix that later.

redoconf/trycompile

@@ -0,0 +1,71 @@
+#!/bin/sh -e
+die() {
+	echo "$0: trycompile: $*" >&2
+	exit 99
+}
+
+ctype=$1
+linktype=$2
+code=$3
+case $ctype in
+	cc)
+		[ -n "$CC" ] || die 'must set $CC first.'
+		useCC="$CC"
+		useCF="$CFLAGS"
+		useExt=".c"
+		;;
+	cxx)
+		[ -n "$CXX" ] || die 'must set $CXX first.'
+		useCC="$CXX"
+		useCF="$CXXFLAGS"
+		useExt=".cc"
+		;;
+	*)
+		die "unknown compile type '$ctype'"
+		;;
+esac
+case $linktype in
+	link|run)
+		[ -n "$LINK" ] || die 'must set $LINK first.'
+		;;
+	nolink)
+		;;
+	*)
+		die "unknown link type '$linktype'"
+		;;
+esac
+base="try.$$.tmp"
+out="$base.o"
+out2="$base.exe"
+src="$base$useExt"
+rm -f "$src" "$out" "$out2"
+set -x
+: "[trycompile]" "$@"
+main=
+[ -n "$RCC_NO_MAIN" ] || main="int main() { return 0; }"
+printf '%s' "
+    $code
+
+    $main
+" >"$src"
+NL="
+"
+IFS="$NL"
+set +e
+set -f
+# We intentionally want to split the variables here,
+# splitting on $NL, so we don't quote them.
+# 'set -f' prevents interpreting wildcards, which
+# we don't want to treat as special.
+(
+	$useCC $CPPFLAGS $useCF -o "$out" -c "$src" || exit
+	if [ "$linktype" = "link" -o "$linktype" = "run" ]; then
+		$LINK $LDFLAGS -o "$out2" "$out" $LIBS || exit
+	fi
+	if [ "$linktype" = "run" ]; then
+		$RUN "./$out2" || exit
+	fi
+)
+rv=$?
+rm -f "$src" "$out" "$out2"
+exit "$rv"