[lldb] Fix FindProcessImpl() for iOS simulators (#139174)

# Benefit

This patch fixes:
1. After `platform select ios-simulator`, `platform process list` will
now print processes which are running in the iOS simulator. Previously,
no process will be listed.
2. After `platform select ios-simulator`, `platform attach --name
<name>` will succeed. Previously, it will error out saying no process is
found.


# Several bugs that is being fixed

1. During the process listing, add `aarch64` to the list of CPU types
for which iOS simulators are checked for.
2. Given a candidate process, when checking for simulators, the original
code will find the desired environment variable (`SIMULATOR_UDID`) and
set the OS to iOS, but then the immediate next environment variable will
set it back to macOS.
3. For processes running on simulator, set the triple's `Environment` to
`Simulator`, so that such processes can pass the filtering [in this
line](https://fburl.com/8nivnrjx). The original code leave it as the
default `UnknownEnvironment`.



# Manual test

**With this patch:**
```
royshi-mac-home ~/public_llvm/build % bin/lldb
(lldb) platform select ios-simulator

(lldb) platform process list
240 matching processes were found on "ios-simulator"

PID    PARENT USER       TRIPLE                         NAME
====== ====== ========== ============================== ============================
40511  28844  royshi     arm64-apple-ios-simulator      FocusPlayground // my toy iOS app running on simulator
... // omit
28844  1      royshi     arm64-apple-ios-simulator      launchd_sim

(lldb) process attach --name FocusPlayground
Process 40511 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
    frame #0: 0x0000000104e3cb70 libsystem_kernel.dylib`mach_msg2_trap + 8
libsystem_kernel.dylib`mach_msg2_trap:
->  0x104e3cb70 <+8>: ret
... // omit
```

**Without this patch:**
```
$ bin/lldb
(lldb) platform select ios-simulator

(lldb) platform process list
error: no processes were found on the "ios-simulator" platform

(lldb) process attach --name FocusPlayground
error: attach failed: could not find a process named FocusPlayground
```


# Unittest

See PR.

lldb/source/Host/macosx/objcxx/Host.mm

@@ -595,7 +595,9 @@ static bool GetMacOSXProcessArgs(const ProcessInstanceInfoMatch *match_info_ptr,
       const llvm::Triple::ArchType triple_arch = triple.getArch();
       const bool check_for_ios_simulator =
           (triple_arch == llvm::Triple::x86 ||
-           triple_arch == llvm::Triple::x86_64);
+           triple_arch == llvm::Triple::x86_64 ||
+           triple_arch == llvm::Triple::aarch64);
+
       const char *cstr = data.GetCStr(&offset);
       if (cstr) {
         process_info.GetExecutableFile().SetFile(cstr, FileSpec::Style::native);
@@ -621,21 +623,20 @@ static bool GetMacOSXProcessArgs(const ProcessInstanceInfoMatch *match_info_ptr,
           }
 
           Environment &proc_env = process_info.GetEnvironment();
-          while ((cstr = data.GetCStr(&offset))) {
-            if (cstr[0] == '\0')
-              break;
-
-            if (check_for_ios_simulator) {
-              if (strncmp(cstr, "SIMULATOR_UDID=", strlen("SIMULATOR_UDID=")) ==
-                  0)
-                process_info.GetArchitecture().GetTriple().setOS(
-                    llvm::Triple::IOS);
-              else
-                process_info.GetArchitecture().GetTriple().setOS(
-                    llvm::Triple::MacOSX);
-            }
-
-            proc_env.insert(cstr);
+          bool is_simulator = false;
+          llvm::StringRef env_var;
+          while (!(env_var = data.GetCStr(&offset)).empty()) {
+            if (check_for_ios_simulator &&
+                env_var.starts_with("SIMULATOR_UDID="))
+              is_simulator = true;
+            proc_env.insert(env_var);
+          }
+          llvm::Triple &triple = process_info.GetArchitecture().GetTriple();
+          if (is_simulator) {
+            triple.setOS(llvm::Triple::IOS);
+            triple.setEnvironment(llvm::Triple::Simulator);
+          } else {
+            triple.setOS(llvm::Triple::MacOSX);
           }
           return true;
         }
@@ -741,8 +742,8 @@ uint32_t Host::FindProcessesImpl(const ProcessInstanceInfoMatch &match_info,
         !match_info.ProcessIDsMatch(process_info))
       continue;
 
-    // Get CPU type first so we can know to look for iOS simulator is we have
-    // x86 or x86_64
+    // Get CPU type first so we can know to look for iOS simulator if we have
+    // a compatible type.
     if (GetMacOSXProcessCPUType(process_info)) {
       if (GetMacOSXProcessArgs(&match_info, process_info)) {
         if (match_info.Matches(process_info))