unix: Enable modbluetooth on the "dev" and "coverage" variants.

And MICROPY_PY_URANDOM_EXTRA_FUNCS is enabled on "dev" so tha the Bluetooth
examples all run.

ports/unix/Makefile

@@ -132,19 +132,26 @@ CFLAGS_MOD += -DMICROPY_PY_THREAD=1 -DMICROPY_PY_THREAD_GIL=0
 LDFLAGS_MOD += $(LIBPTHREAD)
 endif
 
+# If the variant enables it and we have libusb, enable BTStack support for USB adaptors.
 ifeq ($(MICROPY_PY_BLUETOOTH),1)
+
+HAVE_LIBUSB := $(shell (which pkg-config > /dev/null && pkg-config --exists libusb-1.0) 2>/dev/null && echo '1')
+ifeq ($(HAVE_LIBUSB),1)
+
 CFLAGS_MOD += -DMICROPY_PY_BLUETOOTH=1
 CFLAGS_MOD += -DMICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE=1
 CFLAGS_MOD += -DMICROPY_PY_BLUETOOTH_GATTS_ON_READ_CALLBACK=1
 
 MICROPY_BLUETOOTH_BTSTACK ?= 1
 MICROPY_BLUETOOTH_BTSTACK_USB ?= 1
-endif
 
 ifeq ($(MICROPY_BLUETOOTH_BTSTACK),1)
 include $(TOP)/extmod/btstack/btstack.mk
 endif
 
+endif
+endif
+
 ifeq ($(MICROPY_PY_FFI),1)
 
 ifeq ($(MICROPY_STANDALONE),1)

ports/unix/variants/coverage/mpconfigvariant.mk

@@ -17,3 +17,4 @@ MICROPY_ROM_TEXT_COMPRESSION = 1
 MICROPY_VFS_FAT = 1
 MICROPY_VFS_LFS1 = 1
 MICROPY_VFS_LFS2 = 1
+MICROPY_PY_BLUETOOTH = 1

ports/unix/variants/dev/mpconfigvariant.h

@@ -26,5 +26,7 @@
 
 #define MICROPY_REPL_EMACS_WORDS_MOVE (1)
 #define MICROPY_REPL_EMACS_EXTRA_WORDS_MOVE (1)
+#define MICROPY_ENABLE_SCHEDULER (1)
 
 #define MICROPY_PY_SYS_SETTRACE (1)
+#define MICROPY_PY_URANDOM_EXTRA_FUNCS (1)

ports/unix/variants/dev/mpconfigvariant.mk

@@ -1,3 +1,5 @@
 PROG ?= micropython-dev
 
 MICROPY_ROM_TEXT_COMPRESSION = 1
+
+MICROPY_PY_BLUETOOTH = 1