try using nosearch to deprioritize api docs in search

lib/spack/docs/Makefile

@@ -59,6 +59,7 @@ upload:
 apidoc:
 	sphinx-apidoc -f -T -o . ../spack
 	sphinx-apidoc -f -T -o . ../llnl
+        ./nosearch-api-docs  # set :nosearch: at top of each file
 
 help:
 	@echo "Please use \`make <target>' where <target> is one of"

lib/spack/docs/nosearch-api-docs

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Set :nosearch: at top of each api doc file
+for filename in {spack,llnl}.*.rst; do
+    $(echo ":nosearch:"; cat $filename) > $filename
+done