fix compilation of USBTMC for libusb < 1.0.22

[hinxx]

Latest asyn w/ USBTMC does not compile on the ancient Centos7 that we use at ESS due to old availability of libusb 1.0.21.

As per https://libusb.sourceforge.io/api-1.0/group__libusb__lib.html#ga1c7862ed8e3f9402033d45307eefba0e.

[AppVeyorBot]

✅ Build asyn 1.0.261 completed (commit 4b03e55ce5 by @)

[MarkRivers]

I am curious why you are having this problem. I have libusb 1.0.21 installed on my CentOS 7 system and asyn builds fine.

[epics@dec1731 ~]$ more /etc/centos-release
CentOS Linux release 7.9.2009 (Core)
[epics@dec1731 ~]$ sudo yum list installed | grep libusb
libusb.x86_64                           1:0.1.4-3.el7                  @base
libusb-devel.x86_64                     1:0.1.4-3.el7                  @base
libusbmuxd.x86_64                       1.0.10-5.el7                   @base
libusbx.x86_64                          1.0.21-1.el7                   @base
libusbx-devel.x86_64                    1.0.21-1.el7                   @base

Do a rebuild of asyn:

[epics@dec1731 ~]$ cd /corvette/home/epics/devel/asyn
[epics@dec1731 asyn]$ make -sj clean
make[epics@dec1731 asyn]$ make -sj
[no errors]

[hinxx]

Strange.

And your config defines DRV_USBTMC = YES?

ifeq ($(DRV_USBTMC),YES)
  SRC_DIRS += $(ASYN)/drvAsynUSBTMC
  asyn_SRCS += drvAsynUSBTMC.c
  asyn_SYS_LIBS += usb-1.0
  DBD += drvAsynUSBTMC.dbd
endif

[MarkRivers]

And your config defines DRV_USBTMC = YES?

Sorry, no it was not defining DRV_USBTMC = YES on CentOS 7. When I do then I reproduce your error.