Only find closest font if system font was not found (#32482)

Summary:
Before f951da9 finding a system font used to return early. In order to allow variants, the referenced patch removed the early return so that variants could be applied later. However, there is no need to find the closest font as we already selected the proper system font. This also fixes a bug with setting a custom font handler via RCTSetDefaultFontHandler whos return could get overwritten by the closest font search.

## Changelog

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[iOS] [Fixed] - Respect RCTSetDefaultFontHandler chosen font

Pull Request resolved: #32482

Reviewed By: ShikaSD

Differential Revision: D33844138

Pulled By: cortinico

fbshipit-source-id: 05c01fc358cd19f8be342218cdba944b303073ed

React/Views/RCTFont.mm

@@ -355,16 +355,18 @@ + (UIFont *)updateFont:(UIFont *)font
     }
   }
 
-  // Get the closest font that matches the given weight for the fontFamily
-  CGFloat closestWeight = INFINITY;
   NSArray<NSString *> *names = fontNamesForFamilyName(familyName);
-  for (NSString *name in names) {
-    UIFont *match = [UIFont fontWithName:name size:fontSize];
-    if (isItalic == isItalicFont(match) && isCondensed == isCondensedFont(match)) {
-      CGFloat testWeight = weightOfFont(match);
-      if (ABS(testWeight - fontWeight) < ABS(closestWeight - fontWeight)) {
-        font = match;
-        closestWeight = testWeight;
+  if (!didFindFont) {
+    // Get the closest font that matches the given weight for the fontFamily
+    CGFloat closestWeight = INFINITY;
+    for (NSString *name in names) {
+      UIFont *match = [UIFont fontWithName:name size:fontSize];
+      if (isItalic == isItalicFont(match) && isCondensed == isCondensedFont(match)) {
+        CGFloat testWeight = weightOfFont(match);
+        if (ABS(testWeight - fontWeight) < ABS(closestWeight - fontWeight)) {
+          font = match;
+          closestWeight = testWeight;
+        }
       }
     }
   }