[ios-sdk] Fix docs/distribution scripts

Summary:
Appledoc docset name was referenced twice, and differently. Fixed to use the variable set by common.sh, and fixed
common.sh to set the right name.

Test Plan: Revert Plan:

Reviewers: jacl

Reviewed By: jacl

Differential Revision: https://phabricator.fb.com/D497697

README.mdown

@@ -7,3 +7,4 @@ Except as otherwise noted, the Facebook SDK for iOS is licensed under the Apache
 
 Learn more about about the provided samples, documentation, integrating the SDK into your app, accessing source code, and more at http://developers.facebook.com/ios.
 
+NOTE: By default, the Facebook SDK for iOS is installed in ~/Documents/FacebookSDK. A simple way to test your install is to build and run the project at ~/Documents/FacebookSDK/Samples/JustRequestSample/JustRequestSample.xcodeproj.

scripts/build_documentation.sh

@@ -38,7 +38,7 @@ test -d $FB_SDK_BUILD \
 cd $FB_SDK_SRC
 
 APPLEDOC=appledoc
-DOCSET="$FB_SDK_BUILD"/com.facebook.Facebook-SDK-3_0-for-iOS.docset
+DOCSET="$FB_SDK_BUILD"/"$FB_SDK_DOCSET_NAME"
 
 rm -rf $DOCSET
 

scripts/common.sh

@@ -61,7 +61,7 @@ if [ -z "$FB_SDK_SCRIPT" ]; then
   FB_SDK_FRAMEWORK=$FB_SDK_BUILD/$FB_SDK_FRAMEWORK_NAME
 
   # The name of the docset
-  FB_SDK_DOCSET_NAME=com.facebook.Facebook-iOS-SDK.docset
+  FB_SDK_DOCSET_NAME=com.facebook.Facebook-SDK-3_0-for-iOS.docset
 
   # The path to the framework docs
   FB_SDK_FRAMEWORK_DOCS=$FB_SDK_BUILD/$FB_SDK_DOCSET_NAME