pgsql: Avoid macro clash with LLVM 9.

Avoid macro clash with LLVM 9.

Early previews of LLVM 9 reveal that our Min() macro causes compiler
errors in LLVM headers reached by the #include directives in
llvmjit_inline.cpp.  Let's just undefine it.  Per buildfarm animal
seawasp.  Back-patch to 11.

Reviewed-by: Fabien Coelho, Tom Lane
Discussion: https://postgr.es/m/20190606173216.GA6306%40alvherre.pgsql

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/180825fe43ece9bf13c27929b7fdeec5a457e9c3

Modified Files
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src/backend/jit/llvm/llvmjit_inline.cpp | 3 +++
1 file changed, 3 insertions(+)