Derivgen.pl produces incorrect derived config files when changed parameter is a substring of other parameters

Created by: jordancarlin

While working on #840 (closed), I created a derived config with the following parameters:

deriv noS_rv32gc rv32gc
S_SUPPORTED        0
SSTC_SUPPORTED     0
VIRTMEM_SUPPORTED  0
SVINVAL_SUPPORTED  0
SVADU_SUPPORTED    0

Unexpectedly, this caused the produced configuration to set several other parameters to 0 as well. In addition to the expected ones, it also set ZBS_SUPPORTED, BUS_SUPPORTED, and VECTORED_INTERRUPTS_SUPPORTED to 0.

Turning on the debugging print line, we can see that these all matched with S_SUPPORTED

Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for S_SUPPORTED is localparam logic S_SUPPORTED = 0; // Supervisor mode
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for SSTC_SUPPORTED is localparam logic SSTC_SUPPORTED = 0; // Supervisor-mode timer interrupts
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for SVINVAL_SUPPORTED is localparam logic SVINVAL_SUPPORTED = 0;
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for SVADU_SUPPORTED is localparam logic SVADU_SUPPORTED = 0;
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for S_SUPPORTED is localparam logic BUS_SUPPORTED = 0;
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for VIRTMEM_SUPPORTED is localparam logic VIRTMEM_SUPPORTED = 0;
Hit: new line in /home/jcarlin/cvw/config/deriv/noS_rv32gc/config.vh for S_SUPPORTED is localparam logic VECTORED_INTERRUPTS_SUPPORTED = 0;

Seeing as all of the incorrectly set parameters end with S_SUPPORTED (ZBS_SUPPORTED), I assume the script is simply finding the matching substring while missing the rest of the string before it.