rust: save cargo and CARGO_HOME to variables

During configure, substitute the path of cargo, as well as the
value of CARGO_HOME as variables. This fixes the case where a
user might do:
  make
  sudo make install
Which will cause the cargo bits to be rebuilt, including
re-downloading external crates.

By saving these to variables we can be sure that the same
values are used during make install as were used during
make which prevents the Rust artifacts from being rebuild
during "sudo make install".

configure.ac

@@ -2007,9 +2007,15 @@
           CFLAGS="${CFLAGS} -I../rust/gen/c-headers"
           AC_SUBST(RUST_SURICATA_LIB)
           AC_SUBST(RUST_LDADD)
+	  AC_SUBST([CARGO], [$HAVE_CARGO])
+	  if test "x$CARGO_HOME" = "x"; then
+	    AC_SUBST([CARGO_HOME], [~/.cargo])
+	  else
+	    AC_SUBST([CARGO_HOME], [$CARGO_HOME])
+	  fi
           AC_CHECK_FILES([$srcdir/rust/vendor], [have_rust_vendor="yes"])
           if test "x$have_rust_vendor" = "xyes"; then
-	        rust_vendor_comment=""
+	    rust_vendor_comment=""
           fi
         fi
       fi

rust/Makefile.am

@@ -29,15 +29,17 @@ all-local:
 if HAVE_PYTHON
 	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
 		$(HAVE_PYTHON) ./gen-c-headers.py && \
-		cargo build $(RELEASE) $(FROZEN) --features "$(FEATURES)"
+		CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
+			--features "$(FEATURES)"
 else
 	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		cargo build $(RELEASE) $(FROZEN) --features "$(FEATURES)"
+		CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
+			--features "$(FEATURES)"
 endif
 
 clean-local:
 	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		cargo clean
+		CARGO_HOME=$(CARGO_HOME) $(CARGO) clean
 
 distclean-local:
 	rm -rf vendor
@@ -45,14 +47,14 @@ distclean-local:
 
 check:
 	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		cargo test
+		CARGO_HOME=$(CARGO_HOME) $(CARGO) test
 
 Cargo.lock: Cargo.toml
-	cargo update
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) update
 
 if HAVE_CARGO_VENDOR
 vendor:
-	cargo vendor > /dev/null
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) vendor > /dev/null
 else
 vendor:
 endif