Use FASTR_CXX

Author: Pavel Marek

com.oracle.truffle.r.native/gnur/Makefile.gnur

@@ -111,6 +111,12 @@ else
 CONFIGURE_CC := ""
 endif
 
+ifdef FASTR_CXX
+CONFIGURE_CXX := "CXX=$(FASTR_CXX)"
+else
+CONFIGURE_CXX := ""
+endif
+
 GNUR_HOME_BINARY_UNPACKED_PARENT := $(dir $(GNUR_HOME_BINARY_UNPACKED))
 GNUR_CONFIG_LOG = $(GNUR_HOME_BINARY_UNPACKED)/gnur_configure.log
 GNUR_MAKE_LOG = $(GNUR_HOME_BINARY_UNPACKED)/gnur_make.log
@@ -123,7 +129,7 @@ $(GNUR_HOME_BINARY_UNPACKED)/gnur.done:
 	rm -rf $(GNUR_HOME_BINARY_UNPACKED)
 	mkdir -p $(GNUR_HOME_BINARY_UNPACKED_PARENT)
 	(cd $(GNUR_HOME_BINARY_UNPACKED_PARENT); tar xf R-$(R_VERSION).tar.gz)
-	(cd $(GNUR_HOME_BINARY_UNPACKED); ./configure --with-x=no --with-aqua=no --with-pcre2 $(RECPKGS) $(OS_EXTRA_CONFIGURE_FLAGS) $(CONFIGURE_FC) $(CONFIGURE_CC) --enable-memory-profiling $(GNUR_CONFIG_FLAGS) > $(GNUR_CONFIG_LOG) 2>&1; $(MAKE) -j > $(GNUR_MAKE_LOG) 2>&1) || ((tail -n 50 $(GNUR_CONFIG_LOG) $(GNUR_MAKE_LOG) || true) && exit 1)
+	(cd $(GNUR_HOME_BINARY_UNPACKED); ./configure --with-x=no --with-aqua=no --with-pcre2 $(RECPKGS) $(OS_EXTRA_CONFIGURE_FLAGS) $(CONFIGURE_FC) $(CONFIGURE_CC) $(CONFIGURE_CXX) --enable-memory-profiling $(GNUR_CONFIG_FLAGS) > $(GNUR_CONFIG_LOG) 2>&1; $(MAKE) -j > $(GNUR_MAKE_LOG) 2>&1) || ((tail -n 50 $(GNUR_CONFIG_LOG) $(GNUR_MAKE_LOG) || true) && exit 1)
 	touch $(GNUR_HOME_BINARY_UNPACKED)/gnur.done
 else
 $(GNUR_HOME_BINARY_UNPACKED)/gnur.done: