D87588 broke Debug builds on both Solaris/sparcv9 and Solaris/amd64:
[48/224] Linking CXX executable bin/clang-query FAILED: bin/clang-query [...] Undefined first referenced symbol in file _ZN5clang12ast_matchers17decompositionDeclE lib/libclangDynamicASTMatchers.a(Registry.cpp.o) ld: fatal: symbol referencing errors
This doesn't happen for Release builds or x86_64-pc-linux-gnu Debug builds.
However, from comparison with e.g. linkageSpecDecl it's clear that the definition in clang/lib/ASTMatchers/ASTMatchersInternal.cpp is missing and indeed adding it allows the builds to complete.