Work around ld: unrecognized option '--push-state--no-as-needed'

Make error_code and error_condition constexpr, as proposed in https://cplusplus.github.io/LWG/issue2992

.travis.yml

@@ -109,7 +109,7 @@ matrix:
 
     - os: linux
       compiler: g++-7
-      env: UBSAN=1 TOOLSET=gcc COMPILER=g++-7 CXXSTD=03,11,14,17 UBSAN_OPTIONS=print_stacktrace=1
+      env: UBSAN=1 TOOLSET=gcc COMPILER=g++-7 CXXSTD=03,11,14,17 UBSAN_OPTIONS=print_stacktrace=1 LINKFLAGS=-fuse-ld=gold
       addons:
         apt:
           packages:
@@ -267,7 +267,7 @@ install:
 script:
   - |-
     echo "using $TOOLSET : : $COMPILER ;" > ~/user-config.jam
-  - ./b2 -j3 libs/system/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${UBSAN:+cxxflags=-fsanitize=undefined cxxflags=-fno-sanitize-recover=undefined linkflags=-fsanitize=undefined define=UBSAN=1 debug-symbols=on}
+  - ./b2 -j3 libs/system/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${UBSAN:+cxxflags=-fsanitize=undefined cxxflags=-fno-sanitize-recover=undefined linkflags=-fsanitize=undefined define=UBSAN=1 debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}
 
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appveyor.yml

@@ -36,6 +36,13 @@ environment:
       ADDPATH: C:\cygwin\bin;
       TOOLSET: gcc
       CXXSTD: 03,11
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+      ADDPATH: C:\cygwin64\bin;
+      TOOLSET: gcc
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+      ADDPATH: C:\cygwin64\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       ADDPATH: C:\mingw\bin;
       TOOLSET: gcc