[syn] Place result directories in sub-directory

syn/ filling up with result directories is a little annoying, this sets
up the default so everything ends up generated under syn/syn_out/. Flow
users can easily change this to meet their personal requirements.

syn/README.md

@@ -56,11 +56,11 @@ The environment variables that must be set in `syn_setup.sh` are
 # Running the synthesis flow
 
 Once `syn_setup.sh` has been created the `syn_yosys.sh` will run the entire
-flow. All outputs are placed in a directory with the prefix `syn_out_` with the
-current date/time forming the rest of the name, e.g.
-`syn_out_06_01_2020_11_19_15`
+flow. All outputs are placed under the `syn/syn_out` directory with the prefix
+`ibex_` with the current date/time forming the rest of the name, e.g.
+`syn/syn_out/ibex_06_01_2020_11_19_15`
 
-- `syn_out_dir`
+- `syn/syn_out/ibex_date`
   - `reports` - All of the generated reports
     - area.rpt - Total area used and per cell instance counts
     - `timing`
@@ -77,6 +77,9 @@ current date/time forming the rest of the name, e.g.
       - ibex_core.[library-name].out.sdc - Generated .sdc timing constraints
         file
 
+If you wish to change the results directory naming or location edit
+`syn_setup.sh` appropriately.
+
 # Timing constraints
 
 Two files specify the timing constraints and timing related settings for the

syn/syn_setup.example.sh

@@ -7,7 +7,7 @@
 if [ $# -eq 1 ]; then
   export LR_SYNTH_OUT_DIR=$1
 elif [ $# -eq 0 ]; then
-  export LR_SYNTH_OUT_DIR_PREFIX=syn_out
+  export LR_SYNTH_OUT_DIR_PREFIX="syn_out/ibex"
   export LR_SYNTH_OUT_DIR=$(date +"${LR_SYNTH_OUT_DIR_PREFIX}_%d_%m_%Y_%H_%M_%S")
 else
   echo "Usage $0 [synth_out_dir]"