Use self contained rust toolchain

configure.ac

@@ -1400,6 +1400,9 @@ AC_SUBST(HAVE_O_CLOEXEC)
 AC_SUBST(HAVE_BUILTIN_PREFETCH)
 AC_SUBST(HAVE_MM_PREFETCH)
 AC_SUBST(HAVE_STRONG_GETAUXVAL)
+AC_SUBST(RUSTUP_HOME,[$RUSTUP_HOME])
+AC_SUBST(CARGO_HOME,[$CARGO_HOME])
+AC_SUBST(CARGO,[$CARGO])
 
 case $host in
   x86_64-pc-linux-gnu)
@@ -1508,4 +1511,9 @@ echo "  CXX           = $CXX"
 echo "  CXXFLAGS      = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
 echo "  LDFLAGS       = $PTHREAD_CFLAGS $HARDENED_LDFLAGS $GPROF_LDFLAGS $LDFLAGS"
 echo "  ARFLAGS       = $ARFLAGS"
+echo "  RUSTUP_HOME   = $RUSTUP_HOME"
+echo "  CARGO         = $CARGO"
+echo "  CARGO_HOME    = $CARGO_HOME"
+echo "  RUST_DEBUG    = $RUST_DEBUG"
+echo "  RUST_TARGET   = $RUST_TARGET"
 echo

depends/config.site.in

@@ -78,3 +78,11 @@ fi
 if test -n "@LDFLAGS@"; then
   LDFLAGS="@LDFLAGS@ $LDFLAGS"
 fi
+
+# TODO: Should we pick these up from configure as the source
+# and use that during depends? 
+# Is it overridable with local defaults?
+
+CARGO=$depends_prefix/bin/cargo
+CARGO_HOME=$depends_prefix/
+RUSTUP_HOME=$depends_prefix/.rustup

lib/Makefile.am

@@ -1,10 +1,11 @@
+# TODO: Refine these vars with graceful swichover to local and
+# ensure it works without them set as well as with them set
+CARGO_HOME ?= 
+RUSTUP_HOME ?= 
 CARGO ?= cargo
-CARGO_HOME ?= $(CARGO_HOME)
-RUSTUP_HOME ?= $(RUSTUP_HOME)
 
 # RUST_TARGET is set from configure
-TARGET ?= $(RUST_TARGET)
-TARGET ?= x86_64-unknown-linux-gnu
+TARGET = $(if $(RUST_TARGET),$(RUST_TARGET),x86_64-unknown-linux-gnu)
 
 # This is set from configure
 RUST_DEBUG ?= 
@@ -21,7 +22,10 @@ CARGO_MANIFEST_PATH = $(abs_srcdir)/Cargo.toml
 
 .PHONY:
 all: 
-	DESTDIR= TARGET_DIR=$(TARGET_DIR) $(CARGO) build \
+	DESTDIR= TARGET_DIR=$(TARGET_DIR) \
+	RUSTUP_HOME=$(RUSTUP_HOME) \
+	CARGO_HOME=$(CARGO_HOME) \
+	$(CARGO) build \
 		--manifest-path "$(CARGO_MANIFEST_PATH)" \
 		--target-dir "$(TARGET_DIR)" \
 		$(if $(DEBUG),,--release) \
@@ -30,6 +34,8 @@ all:
 
 .PHONY:
 clean-local:
+	RUSTUP_HOME=$(RUSTUP_HOME) \
+	CARGO_HOME=$(CARGO_HOME) \
 	$(CARGO) clean \
 		--manifest-path "$(CARGO_MANIFEST_PATH)" \
 		--target-dir "$(TARGET_DIR)" && \