rust: Add rust detection to configure and a target to add binaries

We detect whether we have the rust tooling available (mainly `cargo`)
and enable or disable the rust libraries, plugins and examples when it
is enabled. Since the rest of the Makefiles assumes that executables
have an associated header and C source file, we also needed to add a
target that we can add non-C binaries to.

.gitignore

@@ -64,3 +64,7 @@ doc/lightning*.[1578]
 # Ignore unrelated stuff
 .DS_Store
 .gdb_history
+
+# Rust targets
+target
+Cargo.lock

Makefile

@@ -230,6 +230,8 @@ ALL_TEST_PROGRAMS :=
 ALL_FUZZ_TARGETS :=
 ALL_C_SOURCES :=
 ALL_C_HEADERS := header_versions_gen.h version_gen.h
+# Extra (non C) targets that should be built by default.
+DEFAULT_TARGETS :=
 
 CPPFLAGS += -DBINTOPKGLIBEXECDIR="\"$(shell sh tools/rel.sh $(bindir) $(pkglibexecdir))\""
 CFLAGS = $(CPPFLAGS) $(CWARNFLAGS) $(CDEBUGFLAGS) $(COPTFLAGS) -I $(CCANDIR) $(EXTERNAL_INCLUDE_FLAGS) -I . -I/usr/local/include $(SQLITE3_CFLAGS) $(POSTGRES_INCLUDE) $(FEATURES) $(COVFLAGS) $(DEV_CFLAGS) -DSHACHAIN_BITS=48 -DJSMN_PARENT_LINKS $(PIE_CFLAGS) $(COMPAT_CFLAGS) -DBUILD_ELEMENTS=1
@@ -260,7 +262,7 @@ ifeq ($(HAVE_POSTGRES),1)
 LDLIBS += $(POSTGRES_LDLIBS)
 endif
 
-default: show-flags all-programs all-test-programs doc-all
+default: show-flags all-programs all-test-programs doc-all default-targets
 
 ifneq ($(SUPPRESS_GENERATION),1)
 FORCE = FORCE
@@ -323,6 +325,13 @@ endif
 		$(call VERBOSE,"printgen $@",tools/generate-wire.py -s -P --page impl $($@_args) ${@:.c=.h} `basename $< .csv | sed 's/_exp_/_/'` < $< > $@ && $(call SHA256STAMP,//,)); \
 	fi
 
+RUST_PROFILE ?= debug
+ifeq ($(RUST_PROFILE),release)
+CARGO_OPTS := --release
+else
+CARGO_OPTS :=
+endif
+
 include external/Makefile
 include bitcoin/Makefile
 include common/Makefile
@@ -345,6 +354,9 @@ include contrib/libhsmd_python/Makefile
 ifneq ($(FUZZING),0)
 	include tests/fuzz/Makefile
 endif
+ifneq ($(RUST),0)
+# Add Rust Makefiles here
+endif
 
 # We make pretty much everything depend on these.
 ALL_GEN_HEADERS := $(filter %gen.h,$(ALL_C_HEADERS))
@@ -604,6 +616,7 @@ update-ccan:
 # Now ALL_PROGRAMS is fully populated, we can expand it.
 all-programs: $(ALL_PROGRAMS)
 all-test-programs: $(ALL_TEST_PROGRAMS) $(ALL_FUZZ_TARGETS)
+default-targets: $(DEFAULT_TARGETS)
 
 distclean: clean
 	$(RM) ccan/config.h config.vars
@@ -627,6 +640,7 @@ clean: obsclean
 	find . -name '*gcda' -delete
 	find . -name '*gcno' -delete
 	find . -name '*.nccout' -delete
+	if [ "${RUST}" -eq "1" ]; then cargo clean; fi
 
 # These must both be enabled for update-mocks
 ifeq ($(DEVELOPER)$(EXPERIMENTAL_FEATURES),11)

configure

@@ -109,6 +109,15 @@ default_valgrind_setting()
     fi
 }
 
+default_rust_setting()
+{
+    if cargo --version > /dev/null 2>&1 || [ $? = 0 ]; then
+	echo 1
+    else
+	echo 0
+    fi
+}
+
 set_defaults()
 {
     # Default values, loaded from environment or canned.
@@ -129,6 +138,7 @@ set_defaults()
     VALGRIND=${VALGRIND:-$(default_valgrind_setting)}
     TEST_NETWORK=${TEST_NETWORK:-regtest}
     FUZZING=${FUZZING:-0}
+    RUST=${RUST:-$(default_rust_setting)}
 }
 
 usage()
@@ -167,6 +177,8 @@ usage()
     usage_with_default "--enable/disable-ub-sanitizer" "$UBSAN" "enable" "disable"
     echo "    Compile with undefined behaviour sanitizer"
     usage_with_default "--enable/disable-fuzzing" "$FUZZING" "enable" "disable"
+    echo "    Compile with Rust support"
+    usage_with_default "--enable/disable-rust" "$RUST" "enable" "disable"
     exit 1
 }
 
@@ -222,6 +234,8 @@ for opt in "$@"; do
 	--disable-ub-sanitize) UBSAN=0;;
 	--enable-fuzzing) FUZZING=1;;
 	--disable-fuzzing) FUZZING=0;;
+	--enable-rust) RUST=1;;
+	--disable-rust) RUST=0;;
 	--help|-h) usage;;
 	*)
 	    echo "Unknown option '$opt'" >&2
@@ -430,6 +444,7 @@ add_var TEST_NETWORK "$TEST_NETWORK"
 add_var HAVE_PYTHON3_MAKO "$HAVE_PYTHON3_MAKO"
 add_var SHA256SUM "$SHA256SUM"
 add_var FUZZING "$FUZZING"
+add_var RUST "$RUST"
 
 # Hack to avoid sha256 name clash with libwally: will be fixed when that
 # becomes a standalone shared lib.