docs: update envvars.html to reflect having a cache per arch
diff --git a/docs/envvars.html b/docs/envvars.html
index 9f1f708..aa56cd1 100644
--- a/docs/envvars.html
+++ b/docs/envvars.html
@@ -119,7 +119,10 @@
the on-disk cache of compiled GLSL programs. Should be set to a number
optionally followed by 'K', 'M', or 'G' to specify a size in
kilobytes, megabytes, or gigabytes. By default, gigabytes will be
-assumed. And if unset, a maximum size of 1GB will be used.
+assumed. And if unset, a maximum size of 1GB will be used. Note: A separate
+cache might be created for each architecture that Mesa is installed for on
+your system. For example under the default settings you may end up with a 1GB
+cache for x86_64 and another 1GB cache for i386.
<li>MESA_GLSL_CACHE_DIR - if set, determines the directory to be used
for the on-disk cache of compiled GLSL programs. If this variable is
not set, then the cache will be stored in $XDG_CACHE_HOME/mesa (if