Automatically detect when -luuid is needed (on Linux with tours enabled)

This is done in a cross-compile-friendly manner with cpp rather than
uname. printf is used rather than echo due to inconsistent handling of
the -e option across different shells.

Makefile

@@ -23,6 +23,14 @@ CFLAGS += -DGHASHPREC=$(GHASHPREC)
 LIBS += -llmdb
 LIBS += -lpthread
 
+define CPP_CONDITION
+printf '#if $(1) \n
+true \n
+#else \n
+#error false \n
+#endif' | $(CPP) -P - >/dev/null 2>&1 && echo yes
+endef
+
 ifeq ($(WITH_MQTT),yes)
 	CFLAGS += -DWITH_MQTT=1
 	CFLAGS += $(MOSQUITTO_INC)
@@ -56,6 +64,12 @@ endif
 ifeq ($(WITH_TOURS),yes)
 	CFLAGS += -DWITH_TOURS
 	OTR_EXTRA_OBJS +=
+
+	# Debian requires uuid-dev
+	# RHEL/CentOS needs libuuid-devel
+	ifeq ($(shell $(call CPP_CONDITION,__linux__)),yes)
+		LIBS += -luuid
+	endif
 endif
 
 ifeq ($(WITH_GREENWICH),yes)

config.mk.in

@@ -40,7 +40,7 @@ WITH_MQTT ?= yes
 WITH_HTTP ?= yes
 
 # Do you want recorder support for shared views? Requires WITH_HTTP
-# also requires -luuid on Linux (see below at MORELIBS)
+# also requires -luuid on Linux.
 WITH_TOURS ?= yes
 
 # Do you have Lua libraries installed and want the Lua hook integration?
@@ -93,10 +93,6 @@ CONFIGFILE = /etc/default/ot-recorder
 MOSQUITTO_INC = -I/usr/include
 MOSQUITTO_LIB = -L/usr/lib
 
-# Debian requires uuid-dev
-# RHEL/CentOS needs libuuid-devel
-MORELIBS += -luuid # -lssl
-
 # Milliseconds (ms) timeout for reverse geocoding
 GEOCODE_TIMEOUT = 4000
 

etc/centos/config.mk.in

@@ -19,7 +19,6 @@ GHASHPREC = 7
 JSON_INDENT ?= no
 MOSQUITTO_INC = -I/usr/include
 MOSQUITTO_LIB = -L/usr/lib
-MORELIBS = -luuid # -lssl
 LUA_CFLAGS = `pkg-config --cflags lua`
 LUA_LIBS   = `pkg-config --libs lua`
 

etc/debian/config.mk.in

@@ -19,7 +19,6 @@ GHASHPREC = 7
 JSON_INDENT ?= no
 MOSQUITTO_INC = -I/usr/include
 MOSQUITTO_LIB = -L/usr/lib
-MORELIBS = -luuid # -lssl
 LUA_CFLAGS = `pkg-config --cflags lua`
 LUA_LIBS   = `pkg-config --libs lua`
 SODIUM_CFLAGS = `pkg-config --cflags libsodium`

etc/raspbian/config.mk.in

@@ -20,7 +20,6 @@ GHASHPREC = 7
 JSON_INDENT ?= no
 MOSQUITTO_INC = -I/usr/include
 MOSQUITTO_LIB = -L/usr/lib
-MORELIBS = -luuid # -lssl
 
 LUA_CFLAGS = `pkg-config --cflags lua`
 LUA_LIBS   = `pkg-config --libs lua`