remove pre-generated input corpus for PGO

INSTALL.md

@@ -196,12 +196,32 @@ all code paths in foot is exercised. In particular, the **rendering**
 code is not. As a result, the final binary built using this method is
 slightly slower than when doing a [full PGO](#full-pgo) build.
 
-We will use the `pgo` binary along with stimuli found in `<src>/pgo`:
+We will use the `pgo` binary along with input corpus generated by
+`scripts/generate-alt-random-writes.py`:
 
 ```sh
-./pgo ../../pgo/stimuli-*.raw
+tmp_file=$(mktemp)
+../../scripts/generate-alt-random-writes \
+    --rows=67 \
+    --cols=135 \
+    --scroll \
+    --scroll-region \
+    --colors-regular \
+    --colors-bright \
+    --colors-256 \
+    --colors-rgb \
+    ${tmp_file}
+./pgo ${tmp_file} ${tmp_file} ${tmp_file} ${tmp_file} ${tmp_file} ${tmp_file}
+rm ${tmp_file}
 ```
 
+The snippet above first creates an (empty) temporary file. Then, it
+runs a script that generates random escape sequences (if you cat
+`${tmp_file}` in a terminal, you’ll see random colored characters all
+over the screen). Finally, we feed the randomly generated escape
+sequences to the PGO helper. This is what generates the profiling data
+used in the next step.
+
 You are now ready to [use the generated PGO
 data](#use-the-generated-pgo-data).