Don't allow '~' as the first character in symbol name in linker script.
PR ld/22267
* ldlex.l (SYMBOLNAMECHAR1) New.
(DEFSYMEXP): Replace FILENAMECHAR1 with SYMBOLNAMECHAR1.
(EXPRESSION): Likewise.
* testsuite/ld-scripts/expr.exp: Run pr22267.
* testsuite/ld-scripts/pr22267.d: New file.
* testsuite/ld-scripts/pr22267.s: Likewise.
* testsuite/ld-scripts/pr22267.t: Likewise.