-DFIRMWARE_INSTALL_DIR is not always respected

[MattBlack85]

Describe the bug
While most of the firmwares are correctly moved to the folder specified with the flag, the following ones are not:

Guider_mono_rev16_intel.srec  
gdr_usb.hex
sbigfcam.hex
sbiglcam.hex
sbigpcam.hex
sbigucam.hex
stfga.bin

To Reproduce
run the following command to compile the libs

cmake -DCMAKE_INSTALL_PREFIX=/usr \
      -DCMAKE_BUILD_TYPE=Debug \
      -DFIRMWARE_INSTALL_DIR=/usr/lib/firmware \
      -DBUILD_LIBS=1

Expected behavior
All firmwares should go into /usr/lib/firmware

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: ArchLinux aarch64
• Version 1.9.4