[flang][Lower] Move SymbolBox::dump and SymMap::dump out of line

Fix linking issue in tco and fir-opt, where the inline definitions
generated references to the operator<<, whose definition was not
linked in.

Example:
ld.lld: error: undefined symbol: Fortran::lower::operator<<(llvm::raw_ostream&, Fortran::lower::SymbolBox const&)
>>> referenced by SymbolMap.h:131 (/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/include/flang/Lower/SymbolMap.h:131)
>>>               LowerHLFIRIntrinsics.cpp.o:(Fortran::lower::SymbolBox::dump() const) in archive lib/libHLFIRTransforms.a

Author: kparzysz

flang/include/flang/Lower/SymbolMap.h

@@ -128,7 +128,7 @@ struct SymbolBox : public fir::details::matcher<SymbolBox> {
                                        const SymbolBox &symBox);
 
   /// Dump the map. For debugging.
-  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this << '\n'; }
+  LLVM_DUMP_METHOD void dump() const;
 
 private:
   VT box;
@@ -293,7 +293,7 @@ class SymMap {
                                        const SymMap &symMap);
 
   /// Dump the map. For debugging.
-  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this << '\n'; }
+  LLVM_DUMP_METHOD void dump() const;
 
   void addVariableDefinition(semantics::SymbolRef symRef,
                              fir::FortranVariableOpInterface definingOp,

flang/lib/Lower/SymbolMap.cpp

@@ -82,6 +82,10 @@ Fortran::lower::SymMap::lookupImpliedDo(Fortran::lower::SymMap::AcDoVar var) {
   return {};
 }
 
+void Fortran::lower::SymbolBox::dump() const { llvm::errs() << *this << '\n'; }
+
+void Fortran::lower::SymMap::dump() const { llvm::errs() << *this << '\n'; }
+
 llvm::raw_ostream &
 Fortran::lower::operator<<(llvm::raw_ostream &os,
                            const Fortran::lower::SymbolBox &symBox) {