Reduce binary size

[metarutaiga]

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Issue or Suggestion Description

the Clang has a bad design to collect all unnamed string into .rodata.str?.?
For example, the MbedTLS has many self tests but we don't use it,
But it still keep many string into .rodata.str?.?

llvm-project/clang/lib/CodeGen/CodeGenModule.cpp

Line 7056 in c653766

GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);

to

GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::None); 

After the patch, all unnamed string would be one string per .rodata..L.str.??? section

Then we need to add a line to the linker script [ld.flash.sections] to keep string addresses.

  .flash.rodata : ALIGN(0x10)
  {
    _flash_rodata_start = ABSOLUTE(.);

+    *(.rodata..L.*)    
    SECTION_MAPPINGS(flash_rodata)

So we need a option to control the enum.