Improve debuginfo test coverage for simple statics.

- Re-enabled basic-types-globals which has been disabled since 2018
- Updated its now-rotted assertions about GDB's output to pass
- Rewrote header comment describing some previous state of GDB behavior
  that didn't match either the checked-in assertions _or_ the current
  behavior, and so I assume has just been wrong for some time.
- Copy-pasta'd the test into a version that uses LTO to check for
  regression on #90357, because I don't see a way to matrix the same
  test into several build configurations.

src/test/debuginfo/basic-types-globals-lto.rs

@@ -0,0 +1,80 @@
+// Caveat - gdb doesn't know about UTF-32 character encoding and will print a
+// rust char as only its numerical value.
+
+// min-lldb-version: 310
+
+// no-prefer-dynamic
+// compile-flags:-g -C lto
+// gdb-command:run
+// gdbg-command:print 'basic_types_globals::B'
+// gdbr-command:print B
+// gdb-check:$1 = false
+// gdbg-command:print 'basic_types_globals::I'
+// gdbr-command:print I
+// gdb-check:$2 = -1
+// gdbg-command:print 'basic_types_globals::C'
+// gdbr-command:print C
+// gdbg-check:$3 = 97
+// gdbr-check:$3 = 97
+// gdbg-command:print/d 'basic_types_globals::I8'
+// gdbr-command:print I8
+// gdb-check:$4 = 68
+// gdbg-command:print 'basic_types_globals::I16'
+// gdbr-command:print I16
+// gdb-check:$5 = -16
+// gdbg-command:print 'basic_types_globals::I32'
+// gdbr-command:print I32
+// gdb-check:$6 = -32
+// gdbg-command:print 'basic_types_globals::I64'
+// gdbr-command:print I64
+// gdb-check:$7 = -64
+// gdbg-command:print 'basic_types_globals::U'
+// gdbr-command:print U
+// gdb-check:$8 = 1
+// gdbg-command:print/d 'basic_types_globals::U8'
+// gdbr-command:print U8
+// gdb-check:$9 = 100
+// gdbg-command:print 'basic_types_globals::U16'
+// gdbr-command:print U16
+// gdb-check:$10 = 16
+// gdbg-command:print 'basic_types_globals::U32'
+// gdbr-command:print U32
+// gdb-check:$11 = 32
+// gdbg-command:print 'basic_types_globals::U64'
+// gdbr-command:print U64
+// gdb-check:$12 = 64
+// gdbg-command:print 'basic_types_globals::F32'
+// gdbr-command:print F32
+// gdb-check:$13 = 2.5
+// gdbg-command:print 'basic_types_globals::F64'
+// gdbr-command:print F64
+// gdb-check:$14 = 3.5
+// gdb-command:continue
+
+#![allow(unused_variables)]
+#![feature(omit_gdb_pretty_printer_section)]
+#![omit_gdb_pretty_printer_section]
+
+// N.B. These are `mut` only so they don't constant fold away.
+static mut B: bool = false;
+static mut I: isize = -1;
+static mut C: char = 'a';
+static mut I8: i8 = 68;
+static mut I16: i16 = -16;
+static mut I32: i32 = -32;
+static mut I64: i64 = -64;
+static mut U: usize = 1;
+static mut U8: u8 = 100;
+static mut U16: u16 = 16;
+static mut U32: u32 = 32;
+static mut U64: u64 = 64;
+static mut F32: f32 = 2.5;
+static mut F64: f64 = 3.5;
+
+fn main() {
+    _zzz(); // #break
+
+    let a = unsafe { (B, I, C, I8, I16, I32, I64, U, U8, U16, U32, U64, F32, F64) };
+}
+
+fn _zzz() {()}

src/test/debuginfo/basic-types-globals.rs

@@ -1,11 +1,7 @@
-// Caveats - gdb prints any 8-bit value (meaning rust I8 and u8 values)
-// as its numerical value along with its associated ASCII char, there
-// doesn't seem to be any way around this. Also, gdb doesn't know
-// about UTF-32 character encoding and will print a rust char as only
-// its numerical value.
+// Caveat - gdb doesn't know about UTF-32 character encoding and will print a
+// rust char as only its numerical value.
 
 // min-lldb-version: 310
-// ignore-gdb // Test temporarily ignored due to debuginfo tests being disabled, see PR 47155
 
 // compile-flags:-g
 // gdb-command:run
@@ -18,7 +14,7 @@
 // gdbg-command:print 'basic_types_globals::C'
 // gdbr-command:print C
 // gdbg-check:$3 = 97
-// gdbr-check:$3 = 97 'a'
+// gdbr-check:$3 = 97
 // gdbg-command:print/d 'basic_types_globals::I8'
 // gdbr-command:print I8
 // gdb-check:$4 = 68