Fixed failing Appveyor MinGW builds due to '_hypot' not being defined.

This is caused by a MinGW bug in math.h. See http://ehc.ac/p/mingw/bugs/2250/
for more information.

CMakeLists.txt

@@ -40,6 +40,9 @@ set(GettextTranslate_GMO_BINARY 1)
 
 add_definitions(-DCRITERION_BUILDING_DLL=1)
 
+set(CMAKE_C_FLAGS_DEFAULT "${CMAKE_C_FLAGS}")
+set(CMAKE_CXX_FLAGS_DEFAULT "${CMAKE_CXX_FLAGS}")
+
 if (NOT MSVC)
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -Werror -g -std=gnu99")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror -g -std=c++11")

appveyor.yml

@@ -15,6 +15,7 @@ environment:
   matrix:
   - COMPILER: mingw
     GENERATOR: "MSYS Makefiles"
+    CXXFLAGS: -D__NO_INLINE__
   - COMPILER: msvc
     GENERATOR: "Visual Studio 14 2015"
     CFLAGS: /MP

samples/CMakeLists.txt

@@ -1,6 +1,6 @@
 if (NOT MSVC)
-  set(CMAKE_C_FLAGS "-std=c99 -Wall -Wextra -pedantic")
-  set(CMAKE_CXX_FLAGS "-std=c++11 -Wall -Wextra -pedantic")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS_DEFAULT} -std=c99 -Wall -Wextra -pedantic")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS_DEFAULT} -std=c++11 -Wall -Wextra -pedantic")
 endif ()
 
 include_directories(../include)

test/CMakeLists.txt

@@ -1,6 +1,6 @@
 if (NOT MSVC)
-  set(CMAKE_C_FLAGS "-std=gnu99 -Wall -Wextra")
-  set(CMAKE_CXX_FLAGS "-std=c++11 -Wall -Wextra")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS_DEFAULT} -std=gnu99 -Wall -Wextra")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS_DEFAULT} -std=c++11 -Wall -Wextra")
 endif ()
 
 include_directories(../include ../src)