Use absolute iOS paths in Fastlane

ios/fastlane/Fastfile

@@ -1,4 +1,5 @@
 require "fileutils"
+require "shellwords"
 
 default_platform(:ios)
 
@@ -7,6 +8,9 @@ SCHEME = "Sybil"
 TEAM_ID = "DQQH5H6GBD"
 PROFILE_NAME = "Sybil AppStore CI"
 MATCH_BRANCH = "master"
+IOS_ROOT = File.expand_path("..", __dir__)
+PROJECT_FILE = File.join(IOS_ROOT, "Sybil.xcodeproj")
+PROJECT_SPEC = File.join(IOS_ROOT, "project.yml")
 
 def present?(value)
   !value.to_s.strip.empty?
@@ -97,11 +101,11 @@ platform :ios do
 
     api_key = app_store_api_key
 
-    sh("xcodegen --spec project.yml")
+    sh("xcodegen --spec #{PROJECT_SPEC.shellescape}")
 
     increment_version_number(
       version_number: release_version,
-      xcodeproj: "Sybil.xcodeproj"
+      xcodeproj: PROJECT_FILE
     )
 
     latest_build_number = latest_testflight_build_number(
@@ -112,12 +116,13 @@ platform :ios do
 
     increment_build_number(
       build_number: latest_build_number + 1,
-      xcodeproj: "Sybil.xcodeproj"
+      xcodeproj: PROJECT_FILE
     )
 
     sync_match_signing(readonly: true)
 
     build_app(
+      project: PROJECT_FILE,
       scheme: SCHEME,
       export_method: "app-store",
       export_options: {