Resolve 14506, avoid libidn2 for our curl dependency

bazel/foreign_cc/BUILD

@@ -126,6 +126,8 @@ envoy_cmake_external(
         "CURL_CA_PATH": "none",
         "CMAKE_USE_OPENSSL": "off",
         "OPENSSL_ROOT_DIR": "$EXT_BUILD_DEPS",
+        # Avoid libidn2
+        "USE_LIBIDN2": "off",
         # NGHTTP2.
         "USE_NGHTTP2": "on",
         "NGHTTP2_LIBRARY": "$EXT_BUILD_DEPS/nghttp2",

bazel/foreign_cc/curl.patch

@@ -1,14 +1,61 @@
+#commit 743021d6c7abba91c47e5be8035ff0497f2b78bd
+#Author: Jay Satiro <raysatiro@yahoo.com>
+#Date:   Tue Dec 22 15:31:03 2020 -0500
+#
+#    cmake: Add an option to disable libidn2
+#    
+#    New option USE_LIBIDN2 defaults to ON for libidn2 detection. Prior to
+#    this change libidn2 detection could not be turned off in cmake builds.
+#    
+#    Reported-by: William A Rowe Jr
+#    
+#    Fixes https://github.com/curl/curl/issues/6361
+#    Closes #xxxx
+#
+#commit e952764adbb89f37dbf227a48a55cc57c60b537d
+#Author: William A Rowe Jr <wrowe@vmware.com>
+#Date:   Wed Oct 7 14:32:49 2020 -0500
+#
+#    Correct fragile windows assumptions
+#    
+#    - Locking CMake to 3.16 breaks all features and corrections applied to
+#      CMake 3.17 and later, including the correction of the poorly designed
+#      and now abandoned Windows CRT election policy CMP0091 (see final para
+#      of the policy description here:
+#      https://cmake.org/cmake/help/v3.18/policy/CMP0091.html). Locking to
+#      rev 3.16 from ensures a more difficult transition to CMake-current
+#    
+#    - Windows curl builds previously only adjusted the Release and Debug
+#      builds, and combined with CMP0091 to break other flavors. Update any
+#      /MD* flags with /MT* present in the base and four alternate build
+#      flavors, without introducing conflicting flag values or introducing
+#      a CRT election where one is not present
+#    
+#    - Windows clang-cl builds of curl static libs are broken when using
+#      link-lld.exe because curl appended the dynamic run time flags to the
+#      static library lib.exe options. While these were ignored/no-op on
+#      Windows link.exe, they cause link-lld from LLVM/clang-cl compile
+#      toolchain to fail to parse the library command.
+#    
+#    Summary exists in this bazel-specific bug report;
+#    https://github.com/bazelbuild/rules_foreign_cc/issues/426
 diff --git a/CMakeLists.txt b/CMakeLists.txt
-index ec1cfa782..0c5a72f00 100644
+index 6a1a6fe8e..777ee122f 100644
 --- a/CMakeLists.txt
 +++ b/CMakeLists.txt
-@@ -42,0 +42,5 @@
-+# revert CMake bug triggered by curl's defined max CMake policy version, see https://gitlab.kitware.com/cmake/cmake/-/issues/21288
+@@ -40,4 +40,9 @@
+ cmake_minimum_required(VERSION 3.2...3.16 FATAL_ERROR)
+
++# Revert CMake bug triggered by curl's defined max CMake policy version, see https://gitlab.kitware.com/cmake/cmake/-/issues/21288
 +if(POLICY CMP0091)
 +  cmake_policy(SET CMP0091 OLD)
 +endif()
 +
-@@ -249,3 +254,6 @@
+ set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/CMake;${CMAKE_MODULE_PATH}")
+ include(Utilities)
+@@ -248,7 +253,10 @@ endif()
+
+ if(CURL_STATIC_CRT)
 -  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 -  set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} /MT")
 -  set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} /MTd")
@@ -18,3 +65,16 @@ index ec1cfa782..0c5a72f00 100644
 +      string(REGEX REPLACE "/MD" "/MT" ${flags_var} "${${flags_var}}")
 +    endif()
 +  endforeach()
+ endif()
+
+@@ -619,5 +627,9 @@ endif()
+
+ # Check for idn
+-check_library_exists_concat("idn2" idn2_lookup_ul HAVE_LIBIDN2)
++option(USE_LIBIDN2 "Use libidn2 for IDN support" ON)
++set(HAVE_LIBIDN2 OFF)
++if(USE_LIBIDN2)
++  check_library_exists_concat("idn2" idn2_lookup_ul HAVE_LIBIDN2)
++endif()
+
+ # Check for symbol dlopen (same as HAVE_LIBDL)

bazel/repositories.bzl

@@ -633,12 +633,10 @@ def _com_github_curl():
         build_file_content = BUILD_ALL_CONTENT + """
 cc_library(name = "curl", visibility = ["//visibility:public"], deps = ["@envoy//bazel/foreign_cc:curl"])
 """,
-        # Patch curl 7.72.0 due to CMake's problematic implementation of policy `CMP0091`
-        # introduced in CMake 3.15 and then deprecated in CMake 3.18. Curl forcing the CMake
-        # ruleset to 3.16 breaks the Envoy windows fastbuild target.
-        # Also cure a fatal assumption creating a static library using LLVM `lld-link.exe`
-        # adding dynamic link flags, which breaks the Envoy clang-cl library archive step.
-        # Upstream patch submitted: https://github.com/curl/curl/pull/6050
+        # Patch curl 7.74.0 due to CMake's problematic implementation of policy `CMP0091`
+        # and introduction of libidn2 dependency which is inconsistently available and must
+        # not be a dynamic dependency on linux.
+        # Upstream patches submitted: https://github.com/curl/curl/pull/6050 & 6362
         # TODO(https://github.com/envoyproxy/envoy/issues/11816): This patch is obsoleted
         # by elimination of the curl dependency.
         patches = ["@envoy//bazel/foreign_cc:curl.patch"],