Convert GN libs lists to frameworks

GN recently added support for Apple frameworks to link, rather than
overloading the libs lists. This pulls .frameworks out of the libs
lists, so that GN can stop supporting .frameworks in libs in the
future.

Bug: chromium:1052560
Change-Id: Icbeb7ffb2e07e182f28d791b22d6979212816ce3
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/71130
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 8bfe0ca55..f22617e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -181,7 +181,7 @@
   }
 
   if (is_mac) {
-    libs += [
+    frameworks = [
       "AppKit.framework",
       "CoreFoundation.framework",
     ]
diff --git a/core/fpdfapi/font/BUILD.gn b/core/fpdfapi/font/BUILD.gn
index c30269a..11f4ece 100644
--- a/core/fpdfapi/font/BUILD.gn
+++ b/core/fpdfapi/font/BUILD.gn
@@ -48,7 +48,7 @@
     "../parser",
   ]
   if (is_mac) {
-    libs = [ "CoreFoundation.framework" ]
+    frameworks = [ "CoreFoundation.framework" ]
   }
   visibility = [ "../../../*" ]
 }
diff --git a/core/fxge/BUILD.gn b/core/fxge/BUILD.gn
index db8b658..9a95141 100644
--- a/core/fxge/BUILD.gn
+++ b/core/fxge/BUILD.gn
@@ -175,7 +175,7 @@
       "apple/fx_quartz_device.cpp",
       "apple/fx_quartz_device.h",
     ]
-    libs = [ "CoreGraphics.framework" ]
+    frameworks = [ "CoreGraphics.framework" ]
   }
 
   if (is_win) {
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index 066108d..2dc32c5 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -327,7 +327,7 @@
   }
 
   if (is_ios) {
-    libs = [ "ImageIO.framework" ]
+    frameworks = [ "ImageIO.framework" ]
     set_sources_assignment_filter([])
     sources += [ "//third_party/skia/src/utils/mac/SkCreateCGImageRef.cpp" ]
     set_sources_assignment_filter(sources_assignment_filter)