Linker script: implement ALIGNOF

Differential revision: https://reviews.llvm.org/D24141

llvm-svn: 280915
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 5b40324..a3732ee 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -127,6 +127,7 @@
 public:
   virtual uint64_t getOutputSectionAddress(StringRef Name) = 0;
   virtual uint64_t getOutputSectionSize(StringRef Name) = 0;
+  virtual uint64_t getOutputSectionAlign(StringRef Name) = 0;
   virtual uint64_t getHeaderSize() = 0;
   virtual uint64_t getSymbolValue(StringRef S) = 0;
 };
@@ -173,6 +174,7 @@
   bool hasPhdrsCommands();
   uint64_t getOutputSectionAddress(StringRef Name) override;
   uint64_t getOutputSectionSize(StringRef Name) override;
+  uint64_t getOutputSectionAlign(StringRef Name) override;
   uint64_t getHeaderSize() override;
   uint64_t getSymbolValue(StringRef S) override;