Building EPICS-VISA with Keysight VISA (Ubuntu 22.04)

I am using a DVM Hp3458A with a Keysight 82350C PCI-GPIB and for this setup, the visa libraries (that worked) are installed using the Linux IO Libraries from Keysight (https://edadocs.software.keysight.com/kkbopen/linux-io-libraries-faq-589309025.html)

In order to make it work with EPICS-VISA I had to point to a different location during the build:

visa_lib.mak:
```
(APPNAME)_SYS_LIBS_Linux += visa -- > $(APPNAME)_SYS_LIBS_Linux += iovisa
```

/VISAdrvApp/src/Makefile:
```
## Linux: the National Instruments visa.h header file location
USR_INCLUDES += -I/usr/include/ni-visa --> USR_INCLUDES += -I/opt/keysight/iolibs/include
```

Is there a way to automate and add these locations ? Since I had also ni-visa installed, which was not working for my device, it was hard to find a solution, because everything was building normally, but communication was not possible. Anyway, I hope this helps other people too.

Inizia con visa_lib.mak e /VISAdrvApp/src/Makefile, concentrandoti sulla libreria VISA esistente e sulle impostazioni per l’inclusione degli header. Confronta i percorsi di NI VISA con le posizioni di Keysight Linux IO Libraries descritte nell’issue. Il lavoro è completato quando la build può selezionare automaticamente l’installazione appropriata senza produrre silenziosamente una configurazione inutilizzabile.

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