cmInstrumentationCommand: Use cmJSONState to read content args

This approach will be more portable.

Source/cmInstrumentationCommand.cxx

@@ -10,7 +10,6 @@ file LICENSE.rst or https://cmake.org/licensing for details.  */
 
 #include <cmext/string_view>
 
-#include <cm3p/json/reader.h>
 #include <cm3p/json/value.h>
 
 #include "cmsys/String.h"
@@ -20,6 +19,7 @@ file LICENSE.rst or https://cmake.org/licensing for details.  */
 #include "cmExecutionStatus.h"
 #include "cmInstrumentation.h"
 #include "cmInstrumentationQuery.h"
+#include "cmJSONState.h"
 #include "cmList.h"
 #include "cmMakefile.h"
 #include "cmMessageType.h"
@@ -206,11 +206,11 @@ bool cmInstrumentationCommand(std::vector<std::string> const& args,
         value.append(item);
       }
     } else if (type == "JSON") {
-      Json::CharReaderBuilder builder;
       std::istringstream iss(contentString);
-      if (!Json::parseFromStream(builder, iss, &value, nullptr)) {
-        status.SetError(
-          cmStrCat("failed to parse custom content as JSON: ", contentString));
+      cmJSONState parseState(iss, &value, cmJSONState::StrictMode::Relaxed);
+      if (!parseState.errors.empty()) {
+        status.SetError(cmStrCat("failed to parse custom content as JSON:\n ",
+                                 parseState.GetErrorMessage()));
         return false;
       }
     } else {

Tests/RunCMake/Instrumentation/cmake-command-custom-content-bad-content-stderr.txt

@@ -1,6 +1,15 @@
 CMake Error at [^
 ]*:1 \(cmake_instrumentation\):
-  cmake_instrumentation failed to parse custom content as JSON: Not valid
-  JSON content
+  cmake_instrumentation failed to parse custom content as JSON:
+(
+   Syntax error: value, object or array expected\.
+
+  Not valid JSON content
+
+  \^|
+   JSON Parse Error:
+   \* Line 1, Column 1
+    Syntax error: value, object or array expected\.
+)
 Call Stack \(most recent call first\):
   CMakeLists\.txt:[0-9]+ \(include\)