[BOLT] Remove redundant declarations (NFC) (#166893)

In C++17, static constexpr members are implicitly inline, so they no
longer require an out-of-line definition.

Identified with readability-redundant-declaration.

Author: kazutakahirata

bolt/lib/Core/BinaryBasicBlock.cpp

@@ -22,8 +22,6 @@
 namespace llvm {
 namespace bolt {
 
-constexpr uint32_t BinaryBasicBlock::INVALID_OFFSET;
-
 bool operator<(const BinaryBasicBlock &LHS, const BinaryBasicBlock &RHS) {
   return LHS.Index < RHS.Index;
 }

bolt/lib/Core/DynoStats.cpp

@@ -51,8 +51,6 @@ PrintDynoOpcodeStat("print-dyno-opcode-stats",
 namespace llvm {
 namespace bolt {
 
-constexpr const char *DynoStats::Desc[];
-
 bool DynoStats::operator<(const DynoStats &Other) const {
   return std::lexicographical_compare(
       &Stats[FIRST_DYNO_STAT], &Stats[LAST_DYNO_STAT],

bolt/lib/Profile/DataAggregator.cpp

@@ -159,8 +159,6 @@ std::vector<SectionNameAndRange> getTextSections(const BinaryContext *BC) {
 }
 }
 
-constexpr uint64_t DataAggregator::KernelBaseAddr;
-
 DataAggregator::~DataAggregator() { deleteTempFiles(); }
 
 namespace {

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -295,7 +295,6 @@ cl::bits<GadgetScannerKind> GadgetScannersToRun(
 } // namespace opts
 
 // FIXME: implement a better way to mark sections for replacement.
-constexpr const char *RewriteInstance::SectionsToOverwrite[];
 std::vector<std::string> RewriteInstance::DebugSectionsToOverwrite = {
     ".debug_abbrev", ".debug_aranges",  ".debug_line",   ".debug_line_str",
     ".debug_loc",    ".debug_loclists", ".debug_ranges", ".debug_rnglists",