Replace $(shell find | sort) with $(sort $(shell find))

Kati's find emulator doesn't understand "| sort", so use use the make
function instead so that we can emulate the find commands.

 before: *kati*: shell time (regen): 1.316989 / 187
 after:  *kati*: shell time (regen): 1.249748 / 184

The time has a lot of variance, the important change is the reduction in
number of shell commands. Kati has other issues with some of these (it
doesn't support find's implicit -a), which is why it only goes down by
3. I'll be fixing Kati separately to handle those cases.

Test: diff out/build-aosp_taimen.ninja before&after
Change-Id: I5c8c2993f01a8a6af84963e903a8a0c186a61e82
diff --git a/core/aux_config.mk b/core/aux_config.mk
index bdae86a..6a5cd63 100644
--- a/core/aux_config.mk
+++ b/core/aux_config.mk
@@ -154,7 +154,7 @@
 config_roots := $(wildcard device vendor)
 all_configs :=
 ifdef config_roots
-all_configs := $(shell find $(config_roots) -maxdepth 4 -name '*$(variant_sfx)' -o -name '*$(os_sfx)' | sort)
+all_configs := $(sort $(shell find $(config_roots) -maxdepth 4 -name '*$(variant_sfx)' -o -name '*$(os_sfx)'))
 endif
 all_os_configs := $(filter %$(os_sfx),$(all_configs))
 all_variant_configs := $(filter %$(variant_sfx),$(all_configs))