ease building with / without randomx

Makefile

@@ -56,8 +56,9 @@ MONERO_LIBS = \
   ${MONERO_BUILD_ROOT}/src/ringct/libringct_basic.a \
   ${MONERO_BUILD_ROOT}/src/device/libdevice.a \
   ${MONERO_BUILD_ROOT}/contrib/epee/src/libepee.a \
-  ${MONERO_BUILD_ROOT}/external/easylogging++/libeasylogging.a \
-  ${MONERO_BUILD_ROOT}/external/randomx/librandomx.a
+  ${MONERO_BUILD_ROOT}/external/easylogging++/libeasylogging.a
+
+LIBRX = ${MONERO_BUILD_ROOT}/external/randomx/librandomx.a
 
 DIRS = src data rxi/log/src
 
@@ -65,6 +66,15 @@ OS := $(shell uname -s)
 
 CPPDEFS = _GNU_SOURCE AUTO_INITIALIZE_EASYLOGGINGPP LOG_USE_COLOR
 
+ifeq ($(wildcard ${LIBRX}),${LIBRX})
+  MONERO_LIBS += ${LIBRX}
+  CPPDEFS += HAVE_RX
+else
+  ifneq ($(MAKECMDGOALS),clean)
+    $(warning Building without RandomX!)
+  endif
+endif
+
 W = -W -Wall -Wno-unused-parameter -Wuninitialized
 OPT = -maes -fPIC
 CFLAGS = $(W) -Wbad-function-cast $(OPT) -std=c99

src/pool.c

@@ -248,8 +248,13 @@ static FILE *fd_log;
 static unsigned char sec_view[32];
 static unsigned char pub_spend[32];
 
+#ifdef HAVE_RX
 extern void rx_stop_mining();
 extern void rx_slow_hash_free_state();
+#else
+void rx_stop_mining(){}
+void rx_slow_hash_free_state(){}
+#endif
 
 #define JSON_GET_OR_ERROR(name, parent, type, client)                \
     json_object *name = NULL;                                        \

src/xmr.cpp

@@ -105,13 +105,15 @@ void get_rx_hash(const unsigned char *input, const size_t in_size,
         unsigned char *output, const unsigned char *seed_hash,
         const uint64_t height)
 {
-    static unsigned max_concurrency = 1;//tools::get_max_concurrency();
+#ifdef HAVE_RX
+    static unsigned max_concurrency = tools::get_max_concurrency();
     uint64_t seed_height;
     if (rx_needhash(height, &seed_height))
     {
         rx_seedhash(seed_height, (const char*)seed_hash, max_concurrency);
     }
     rx_slow_hash((const char*)input, in_size, (char*)output, max_concurrency);
+#endif
 }
 
 int validate_block_from_blob(const char *blob_hex,