Build with the system NSPR library instead of the bundled version.

Originally based on this Debian patch:
https://salsa.debian.org/chromium-team/chromium/-/blob/master/debian/patches/system/nspr.patch

diff --git a/base/BUILD.gn b/base/BUILD.gn
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -141,6 +141,12 @@ config("perfetto_config") {
   }
 }
 
+if (is_linux) {
+  ldflags = [
+    "-lnspr4",
+  ]
+}
+
 # Base and everything it depends on should be a static library rather than
 # a source set. Base is more of a "library" in the classic sense in that many
 # small parts of it are used in many different contexts. This combined with a
@@ -759,8 +765,6 @@ component("base") {
     "third_party/cityhash_v103/src/city_v103.cc",
     "third_party/cityhash_v103/src/city_v103.h",
     "third_party/icu/icu_utf.h",
-    "third_party/nspr/prtime.cc",
-    "third_party/nspr/prtime.h",
     "third_party/superfasthash/superfasthash.c",
     "thread_annotations.h",
     "threading/hang_watcher.cc",
diff --git a/base/time/pr_time_unittest.cc b/base/time/pr_time_unittest.cc
--- a/base/time/pr_time_unittest.cc
+++ b/base/time/pr_time_unittest.cc
@@ -7,7 +7,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/cxx17_backports.h"
-#include "base/third_party/nspr/prtime.h"
+#include <nspr/prtime.h>
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
diff --git a/base/time/time.cc b/base/time/time.cc
--- a/base/time/time.cc
+++ b/base/time/time.cc
@@ -18,7 +18,7 @@
 #include <utility>
 
 #include "base/strings/stringprintf.h"
-#include "base/third_party/nspr/prtime.h"
+#include <nspr/prtime.h>
 #include "base/time/time_override.h"
 #include "build/build_config.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"