check-flagged-apis.sh: use correct path to generated API signature files

The path to the generated API signature files used with --api-signature
in the check-flagged-apis.sh script are different based on the lunch
target used: sometimes it's under $ANDROID_PRODUCT_OUT, other times
under out/target/product/mainline_x86.

Teach check-flagged-apis.sh to dynamically find the correct path by
querying ninja.

Bug: 334870672
Test: croot && build/tools/check-flagged-apis/check-flagged-apis.sh
Change-Id: I1b0b41ef3ad1bc7113a3b31323d81251e7e65933
diff --git a/tools/check-flagged-apis/check-flagged-apis.sh b/tools/check-flagged-apis/check-flagged-apis.sh
index cd37a2d..3399583 100755
--- a/tools/check-flagged-apis/check-flagged-apis.sh
+++ b/tools/check-flagged-apis/check-flagged-apis.sh
@@ -34,12 +34,21 @@
         frameworks-base-api-module-lib-current.txt
 }
 
+function aninja() {
+    local T="$(gettop)"
+    (\cd "${T}" && prebuilts/build-tools/linux-x86/bin/ninja -f out/combined-${TARGET_PRODUCT}.ninja "$@")
+}
+
+function path_to_api_signature_file {
+    aninja -t query device_"$1"_all_targets | grep -A1 -e input: | tail -n1
+}
+
 function run() {
     local errors=0
 
     echo "# current"
     check-flagged-apis \
-        --api-signature $(gettop)/out/target/product/mainline_x86/obj/ETC/frameworks-base-api-current.txt_intermediates/frameworks-base-api-current.txt \
+        --api-signature $(path_to_api_signature_file "frameworks-base-api-current.txt") \
         --flag-values $(gettop)/out/soong/.intermediates/all_aconfig_declarations.pb \
         --api-versions $(gettop)/out/dist/data/api-versions.xml
     (( errors += $? ))
@@ -47,7 +56,7 @@
     echo
     echo "# system-current"
     check-flagged-apis \
-        --api-signature $(gettop)/out/target/product/mainline_x86/obj/ETC/frameworks-base-api-system-current.txt_intermediates/frameworks-base-api-system-current.txt \
+        --api-signature $(path_to_api_signature_file "frameworks-base-api-system-current.txt") \
         --flag-values $(gettop)/out/soong/.intermediates/all_aconfig_declarations.pb \
         --api-versions $(gettop)/out/dist/system-data/api-versions.xml
     (( errors += $? ))
@@ -55,7 +64,7 @@
     echo
     echo "# system-server-current"
     check-flagged-apis \
-        --api-signature $(gettop)/out/target/product/mainline_x86/obj/ETC/frameworks-base-api-system-server-current.txt_intermediates/frameworks-base-api-system-server-current.txt \
+        --api-signature $(path_to_api_signature_file "frameworks-base-api-system-server-current.txt") \
         --flag-values $(gettop)/out/soong/.intermediates/all_aconfig_declarations.pb \
         --api-versions $(gettop)/out/dist/system-server-data/api-versions.xml
     (( errors += $? ))
@@ -63,7 +72,7 @@
     echo
     echo "# module-lib"
     check-flagged-apis \
-        --api-signature $(gettop)/out/target/product/mainline_x86/obj/ETC/frameworks-base-api-module-lib-current.txt_intermediates/frameworks-base-api-module-lib-current.txt \
+        --api-signature $(path_to_api_signature_file "frameworks-base-api-module-lib-current.txt") \
         --flag-values $(gettop)/out/soong/.intermediates/all_aconfig_declarations.pb \
         --api-versions $(gettop)/out/dist/module-lib-data/api-versions.xml
     (( errors += $? ))