Enable PCH on travis builds. Fix error.

.travis.yml

@@ -26,6 +26,6 @@ install:
 
 script:
   - phpize
-  - ./configure --enable-arma-operators
+  - ./configure --enable-arma-operators --enable-arma-pch
   - make -j$(nproc)
   - make test

config.m4

@@ -15,17 +15,17 @@ if test "$PHP_ARMA" != "no"; then
     CXX_INCLEDE_PATHS=($(echo | $CXX -xc++ -E -v - 2>&1 | grep -e '^ /\S*$'))
     PCH_FILE='./build/armadillo.gch'
     # Note that '-D' option is valid when compiling PCH header, but not when using it.
-    CXX_TMP_COMPILE_FLAGS=(-std=c++11 -xc++-header -DARMA_DONT_PRINT_ERRORS -fPIC -c)
+    PCH_COMPILE_FLAGS=(-std=c++17 -xc++-header -DARMA_DONT_PRINT_ERRORS -fPIC -g)
     if test -z "$PHP_DEBUG"; then
-      CXX_TMP_COMPILE_FLAGS+=(-O2)
+      PCH_COMPILE_FLAGS+=(-O0)
     else
-      CXX_TMP_COMPILE_FLAGS+=(-g -O0)
+      PCH_COMPILE_FLAGS+=(-O2)
     fi
   fi
   for POSSIBLE_INCLUDE_DIR in ${CXX_INCLEDE_PATHS[[@]]}; do
     ARMADILLO_HEADER_FILE=$POSSIBLE_INCLUDE_DIR/armadillo
     if test -f "$ARMADILLO_HEADER_FILE"; then
-      $CXX ${CXX_TMP_COMPILE_FLAGS[[@]]} $ARMADILLO_HEADER_FILE -o $PCH_FILE
+      $CXX ${PCH_COMPILE_FLAGS[[@]]} $ARMADILLO_HEADER_FILE -o $PCH_FILE
       break
     fi
   done