Enable PSM libs tests for ChromeOS only until rand_r error is fixed.

Bug: chromium:1124018
Change-Id: Ib9e9f3a5bcb93d9dc094e1daee7217c3e01d8922
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2388603
Commit-Queue: Amr Aboelkher <amraboelkher@chromium.org>
Reviewed-by: Amr Aboelkher <amraboelkher@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803642}

third_party/private_membership/BUILD.gn

@@ -75,7 +75,8 @@ source_set("private_membership") {
   ]
 }
 
-test("private_membership_unittests") {
+if (is_chromeos) {
+  test("private_membership_unittests") {
     testonly = true
     public_configs = [ ":private_membership_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
@@ -100,4 +101,5 @@ test("private_membership_unittests") {
       "//testing/gtest:gtest_main",
       "//third_party/shell-encryption:shell_encryption_test_library",
     ]
+  }
 }

third_party/shell-encryption/BUILD.gn

@@ -94,7 +94,8 @@ source_set("shell_encryption") {
   ]
 }
 
-source_set("shell_encryption_test_library") {
+if (is_chromeos) {
+  source_set("shell_encryption_test_library") {
     testonly = true
     public_configs = [ ":shell_encryption_config1" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
@@ -116,9 +117,9 @@ source_set("shell_encryption_test_library") {
       "//testing/gmock:gmock",
       "//testing/gtest:gtest",
     ]
-}
+  }
 
-source_set("shell_encryption_test") {
+  source_set("shell_encryption_test") {
     testonly = true
     public_configs = [ ":shell_encryption_config1" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
@@ -149,8 +150,9 @@ source_set("shell_encryption_test") {
       ":shell_encryption_test_library",
       "//testing/gtest:gtest_main",
     ]
-}
+  }
 
-test("shell_encryption_unittests") {
+  test("shell_encryption_unittests") {
     deps = [ ":shell_encryption_test" ]
+  }
 }