Use system http-parser, libutf8proc and zxcvbn-c in the bundled SDK.

sdk/third_party carries copies of http-parser 2.6.0, utf8proc 2.1.0 and
zxcvbn-c. Link the system libraries instead and include their headers
from the top-level include directory, where Gentoo installs them.

diff --git a/sdk/cmake/modules/sdklib_libraries.cmake b/sdk/cmake/modules/sdklib_libraries.cmake
index e51fb8e..f8b3868 100644
--- a/sdk/cmake/modules/sdklib_libraries.cmake
+++ b/sdk/cmake/modules/sdklib_libraries.cmake
@@ -9,9 +9,11 @@ macro(load_sdklib_libraries)
     if(NOT HAVE_GLOB_H AND NOT WIN32)
         target_link_libraries(SDKlib PUBLIC glob)
     endif()
-    target_link_libraries(SDKlib PUBLIC http_parser)
-    target_link_libraries(SDKlib PUBLIC utf8proc)
-    target_link_libraries(SDKlib PUBLIC zxcvbn-c)
+    # Gentoo: system net-libs/http-parser, dev-libs/libutf8proc and
+    # dev-libs/zxcvbn-c instead of the copies in third_party/.
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(utf8proc REQUIRED IMPORTED_TARGET libutf8proc)
+    target_link_libraries(SDKlib PUBLIC http_parser PkgConfig::utf8proc zxcvbn)
 
     if(VCPKG_ROOT)
         find_package(cryptopp CONFIG REQUIRED)
diff --git a/sdk/include/mega/utils.h b/sdk/include/mega/utils.h
index 52c1975..db37e7a 100644
--- a/sdk/include/mega/utils.h
+++ b/sdk/include/mega/utils.h
@@ -32,7 +32,7 @@
 #include <thread>
 #include <type_traits>
 #undef SSIZE_MAX
-#include <utf8proc/utf8proc.h>
+#include <utf8proc.h>
 #undef SSIZE_MAX
 
 // Include ICU headers
diff --git a/sdk/include/megaapi_impl.h b/sdk/include/megaapi_impl.h
index ac4491b..25ccdfe 100644
--- a/sdk/include/megaapi_impl.h
+++ b/sdk/include/megaapi_impl.h
@@ -47,7 +47,7 @@
 #ifdef HAVE_LIBUV
 #include "uv.h"
 
-#include <http_parser/http_parser.h>
+#include <http_parser.h>
 
 #ifdef USE_OPENSSL
 #include <evt-tls/evt_tls.h>
diff --git a/sdk/src/filesystem.cpp b/sdk/src/filesystem.cpp
index 2c4320a..23487d4 100644
--- a/sdk/src/filesystem.cpp
+++ b/sdk/src/filesystem.cpp
@@ -29,7 +29,7 @@
 #include "mega/sync.h"
 #include "megafs.h"
 
-#include <utf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include <cassert>
 #include <cctype>
diff --git a/sdk/src/json.cpp b/sdk/src/json.cpp
index acaf0a4..c23936d 100644
--- a/sdk/src/json.cpp
+++ b/sdk/src/json.cpp
@@ -24,7 +24,7 @@
 #include "mega/logging.h"
 #include "mega/megaclient.h"
 
-#include <utf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include <cctype>
 #include <cstdint>
diff --git a/sdk/src/megaapi_impl.cpp b/sdk/src/megaapi_impl.cpp
index baebdb9..7669258 100644
--- a/sdk/src/megaapi_impl.cpp
+++ b/sdk/src/megaapi_impl.cpp
@@ -85,7 +85,7 @@
 #include <openssl/rand.h>
 #endif
 
-#include <zxcvbn-c/zxcvbn.h>
+#include <zxcvbn.h>
 
 // FUSE
 #include <mega/fuse/common/mount_event.h>
diff --git a/sdk/src/utils.cpp b/sdk/src/utils.cpp
index cb8592a..48ee9ba 100644
--- a/sdk/src/utils.cpp
+++ b/sdk/src/utils.cpp
@@ -34,7 +34,7 @@
 #include <unicode/ucol.h>
 #include <unicode/unistr.h>
 #include <unicode/utypes.h>
-#include <utf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include <cctype>
 #include <iomanip>
diff --git a/sdk/third_party/CMakeLists.txt b/sdk/third_party/CMakeLists.txt
index aa1f61b..fd11d08 100644
--- a/sdk/third_party/CMakeLists.txt
+++ b/sdk/third_party/CMakeLists.txt
@@ -6,6 +6,3 @@ endif()
 if(NOT WIN32 AND NOT HAVE_GLOB_H)
 	add_subdirectory(glob)
 endif()
-add_subdirectory(http_parser)
-add_subdirectory(utf8proc)
-add_subdirectory(zxcvbn-c)