Basic: fix compilation with MSVC

Basic: fix compilation with MSVC

MSVC doesn't like the instantiation of the structure in the initializer list.
Initialize it in the constructor body to repair the build.

TargetInfo.h(545) : error C2143: syntax error : missing ')' before '{'
TargetInfo.h(545) : error C2143: syntax error : missing ';' before '}'
TargetInfo.h(545) : error C2059: syntax error : ')'
TargetInfo.h(545) : error C2059: syntax error : ','
TargetInfo.h(547) : error C2143: syntax error : missing ';' before '{'
TargetInfo.h(547) : error C2447: '{' : missing function header (old-style formal list?)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@225247 91177308-0d34-0410-b5e6-96231b3b80d8