[WebAssembly] Assembler: recognize .init_array as data section.

[sbc100]

Can we get a test for this?

[aardappel]

Added test.

lib/MC/MCParser/WasmAsmParser.cpp

if (Lexer->isNot(AsmToken::String))
       return error("expected string in directive, instead got: ", Lexer->getTok());
 
     auto Kind = StringSwitch<Optional<SectionKind>>(Name)
                     .StartsWith(".data", SectionKind::getData())
                     .StartsWith(".rodata", SectionKind::getReadOnly())
                     .StartsWith(".text", SectionKind::getText())
                     .StartsWith(".custom_section", SectionKind::getMetadata())
                     .StartsWith(".bss", SectionKind::getBSS())
+                    // See use of .init_array in WasmObjectWriter and
+                    // TargetLoweringObjectFileWasm
+                    .StartsWith(".init_array", SectionKind::getData())
                     .Default(Optional<SectionKind>());
     if (!Kind.hasValue())
       return Parser->Error(Lexer->getLoc(), "unknown section kind: " + Name);
 
     MCSectionWasm *Section = getContext().getWasmSection(Name, Kind.getValue());
 
     // Update section flags if present in this .section directive
     bool Passive = false;