Change iftable to never be null

Simplifies code generation by removing a null check. The null case
is rare.

Ritzperf code size: 13107624 -> 13095336

Also addressed comments from previous CL.

Bug: 32577579

Test: test-art-host, run ritzperf both with CC

Change-Id: I2b31e800867112869d7f0643e16c08826296979e
diff --git a/compiler/elf_builder.h b/compiler/elf_builder.h
index 31a7529..7c02384 100644
--- a/compiler/elf_builder.h
+++ b/compiler/elf_builder.h
@@ -879,7 +879,7 @@
     elf_header.e_ident[EI_MAG2]       = ELFMAG2;
     elf_header.e_ident[EI_MAG3]       = ELFMAG3;
     elf_header.e_ident[EI_CLASS]      = (sizeof(Elf_Addr) == sizeof(Elf32_Addr))
-                                         ? ELFCLASS32 : ELFCLASS64;;
+                                         ? ELFCLASS32 : ELFCLASS64;
     elf_header.e_ident[EI_DATA]       = ELFDATA2LSB;
     elf_header.e_ident[EI_VERSION]    = EV_CURRENT;
     elf_header.e_ident[EI_OSABI]      = ELFOSABI_LINUX;