Use FORCE_BUILD_LLVM_COMPONENTS.

And remove the allow missing dependencies flag.

Test: build-mainline-modules.sh
Change-Id: I6ba8892ef66eeb42c7bd3abc989a80ad4b6a1cf9

scripts/build-aml-prebuilts.sh

@@ -51,13 +51,11 @@ mkdir -p ${SOONG_OUT}
 SOONG_VARS=${SOONG_OUT}/soong.variables
 
 # We enable bionic linux builds as ART also needs prebuilts for it.
-# Enabling bionic linux requires setting allow_missing_dependencies.
 cat > ${SOONG_VARS}.new << EOF
 {
     "Platform_sdk_version": ${PLATFORM_SDK_VERSION},
     "Platform_sdk_codename": "${PLATFORM_VERSION}",
     "Platform_version_active_codenames": ${PLATFORM_VERSION_ALL_CODENAMES},
-    "Allow_missing_dependencies": true,
 
     "DeviceName": "generic_arm64",
     "HostArch": "x86_64",
@@ -78,4 +76,7 @@ else
   mv ${SOONG_VARS}.new ${SOONG_VARS}
 fi
 
-m --skip-make "$@"
+# We use force building LLVM components flag (even though we actually don't
+# compile them) because we don't have bionic host prebuilts
+# for them.
+FORCE_BUILD_LLVM_COMPONENTS=true m --skip-make "$@"