build: find lto-wrappers where appropriate

configure.ac

@@ -14,23 +14,21 @@ AC_CONFIG_MACRO_DIR([m4])
 AC_USE_SYSTEM_EXTENSIONS
 AC_CANONICAL_HOST
 
-LT_INIT
 AC_LANG([C++])
-AC_PROG_CXX
-AC_PROG_CXXCPP
 
-AX_COMPILER_VENDOR
+NC_CXX
+NC_PLATFORM
+NC_OPTIMISATION
+NC_WARNINGS
+NC_DEBUGGING
+
+LT_INIT
 
 AM_INIT_AUTOMAKE([1.14 dist-bzip2 dist-xz foreign subdir-objects])
 AM_SILENT_RULES([yes])
 
 AC_CONFIG_HEADERS([config.h])
 
-NC_CXX
-NC_PLATFORM
-NC_WARNINGS
-NC_DEBUGGING
-NC_OPTIMISATION
 
 ###############################################################################
 ## Architecture features

m4/nc_optimisation.m4

@@ -2,6 +2,9 @@ AC_DEFUN([NC_OPTIMISATION],[
     ##-------------------------------------------------------------------------
     AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
     AX_REQUIRE_DEFINED([AC_CANONICAL_HOST])
+    AX_REQUIRE_DEFINED([AX_COMPILER_VENDOR])
+
+    AX_COMPILER_VENDOR
 
     ##-------------------------------------------------------------------------
     AC_ARG_ENABLE([lto], [
@@ -13,6 +16,12 @@ AC_DEFUN([NC_OPTIMISATION],[
             AC_ERROR([mingw32 link-time optimisation is currently broken])
         ])
 
+        AS_IF([test "x$ax_cv_cxx_compiler_vendor" == "xgnu"], [
+            AC_CHECK_TOOLS([RANLIB], [gcc-ranlib ranlib])
+            AC_CHECK_TOOLS([AR], [gcc-ar ar])
+            AC_CHECK_TOOLS([NM], [gcc-nm nm])
+        ])
+
         AX_APPEND_COMPILE_FLAGS([-flto], [], [-Werror])
         AX_APPEND_COMPILE_FLAGS([-fno-fat-lto-objects], [], [-Werror])
         AX_APPEND_LINK_FLAGS([-fuse-linker-plugin], [], [-Werror])