Add basic CDB support to debuginfo compiletest s, to help catch `*.natvis` regressions, like those fixed in #60687.

Several Microsoft debuggers (VS, VS Code, WinDbg, CDB, ...) consume the `*.natvis` files we embed into rust `*.pdb` files.
While this only tests CDB, that test coverage should help for all of them.

CHANGES

src\bootstrap
  - test.rs:  Run CDB debuginfo tests on MSVC targets

src\test\debuginfo
  - issue-13213.rs:  CDB has trouble with this, skip for now (newly discovered regression?)
  - pretty-std.rs:  Was ignored, re-enable for CDB only to start with, add CDB tests.
  - should-fail.rs:  Add CDB tests.

src\tools\compiletest:
  - Added "-cdb" option
  - Added Mode::DebugInfoCdb ("debuginfo-cdb")
  - Added run_debuginfo_cdb_test[_no_opt]
  - Renamed Mode::DebugInfoBoth -> DebugInfoGdbLldb ("debuginfo-gdb+lldb") since it's no longer clear what "Both" means.
  - Find CDB at the default Win10 SDK install path "C:\Program Files (x86)\Windows Kits\10\Debugger\*\cdb.exe"
  - Ignore CDB tests if CDB not found.

ISSUES

  - `compute_stamp_hash`: not sure if there's any point in hashing `%ProgramFiles(x86)%`
  - `OsString` lacks any `*.natvis` entries (would be nice to add in a followup changelist)
  - DSTs (array/string slices) which work in VS & VS Code fail in CDB.
  - I've avoided `Mode::DebugInfoAll` as 3 debuggers leads to pow(2,3)=8 possible combinations.

REFERENCE

CDB is not part of the base Visual Studio install, but can be added via the Windows 10 SDK:
  https://developer.microsoft.com/en-us/windows/downloads/windows-10-sdk
Installing just "Debugging Tools for Windows" is sufficient.

CDB appears to already be installed on appveyor CI, where this changelist can find it, based on it's use here:
  https://github.com/rust-lang/rust/blob/0ffc57311030a1930edfa721fe57d0000a063af4/appveyor.yml#L227

CDB commands and command line reference:
  https://docs.microsoft.com/en-us/windows-hardware/drivers/debugger/debugger-reference

3 files changed, 59 insertions, 2 deletions

diff --git a/src/test/debuginfo/issue-13213.rs b/src/test/debuginfo/issue-13213.rs
index 3c9a365fd4f..393478460d4 100644
--- a/src/test/debuginfo/issue-13213.rs
+++ b/src/test/debuginfo/issue-13213.rs
@@ -1,4 +1,5 @@
 // min-lldb-version: 310
+// ignore-cdb: Fails with exit code 0xc0000135 ("the application failed to initialize properly")
 
 // aux-build:issue-13213-aux.rs
 
diff --git a/src/test/debuginfo/pretty-std.rs b/src/test/debuginfo/pretty-std.rs
index 82802eff08a..f568371d68a 100644
--- a/src/test/debuginfo/pretty-std.rs
+++ b/src/test/debuginfo/pretty-std.rs
@@ -1,6 +1,5 @@
-// ignore-windows failing on win32 bot
 // ignore-freebsd: gdb package too new
-// ignore-test // Test temporarily ignored due to debuginfo tests being disabled, see PR 47155
+// only-cdb // Test temporarily ignored on GDB/LLDB due to debuginfo tests being disabled, see PR 47155
 // ignore-android: FIXME(#10381)
 // compile-flags:-g
 // min-gdb-version 7.7
@@ -63,6 +62,56 @@
 // lldb-check:[...]$5 = None
 
 
+// === CDB TESTS ==================================================================================
+
+// cdb-command: g
+
+// cdb-command: dx slice,d
+// cdb-check:slice,d [...]
+// NOTE: While slices have a .natvis entry that works in VS & VS Code, it fails in CDB 10.0.18362.1
+
+// cdb-command: dx vec,d
+// cdb-check:vec,d [...] : { size=4 } [Type: [...]::Vec<u64>]
+// cdb-check:    [size]           : 4 [Type: [...]]
+// cdb-check:    [capacity]       : [...] [Type: [...]]
+// cdb-check:    [0]              : 4 [Type: unsigned __int64]
+// cdb-check:    [1]              : 5 [Type: unsigned __int64]
+// cdb-check:    [2]              : 6 [Type: unsigned __int64]
+// cdb-check:    [3]              : 7 [Type: unsigned __int64]
+
+// cdb-command: dx str_slice
+// cdb-check:str_slice [...]
+// NOTE: While string slices have a .natvis entry that works in VS & VS Code, it fails in CDB 10.0.18362.1
+
+// cdb-command: dx string
+// cdb-check:string           : "IAMA string!" [Type: [...]::String]
+// cdb-check:    [<Raw View>]     [Type: [...]::String]
+// cdb-check:    [size]           : 0xc [Type: [...]]
+// cdb-check:    [capacity]       : 0xc [Type: [...]]
+// cdb-check:    [0]              : 73 'I' [Type: char]
+// cdb-check:    [1]              : 65 'A' [Type: char]
+// cdb-check:    [2]              : 77 'M' [Type: char]
+// cdb-check:    [3]              : 65 'A' [Type: char]
+// cdb-check:    [4]              : 32 ' ' [Type: char]
+// cdb-check:    [5]              : 115 's' [Type: char]
+// cdb-check:    [6]              : 116 't' [Type: char]
+// cdb-check:    [7]              : 114 'r' [Type: char]
+// cdb-check:    [8]              : 105 'i' [Type: char]
+// cdb-check:    [9]              : 110 'n' [Type: char]
+// cdb-check:    [10]             : 103 'g' [Type: char]
+// cdb-check:    [11]             : 33 '!' [Type: char]
+
+// cdb-command: dx os_string
+// cdb-check:os_string        [Type: [...]::OsString]
+// NOTE: OsString doesn't have a .natvis entry yet.
+
+// cdb-command: dx some
+// cdb-check:some             : { Some 8 } [Type: [...]::Option<i16>]
+// cdb-command: dx none
+// cdb-check:none             : { None } [Type: [...]::Option<i64>]
+// cdb-command: dx some_string
+// cdb-check:some_string      : { Some "IAMA optional string!" } [Type: [...]::Option<[...]::String>]
+
 #![allow(unused_variables)]
 use std::ffi::OsString;
 
diff --git a/src/test/debuginfo/should-fail.rs b/src/test/debuginfo/should-fail.rs
index 8765c018b10..1e0d22cbce4 100644
--- a/src/test/debuginfo/should-fail.rs
+++ b/src/test/debuginfo/should-fail.rs
@@ -18,6 +18,13 @@
 // lldb-command:print x
 // lldb-check:[...]$0 = 5
 
+// === CDB TESTS ==================================================================================
+
+// cdb-command:g
+
+// cdb-command:dx x
+// cdb-check:string [...] : 5 [Type: [...]]
+
 fn main() {
     let x = 1;