travis: add compilation to SOURCE_CHECK_ONLY.

Our "-O3" CI check wasn't doing what I thought.  But building with -flto
is hard with older gccs, so remove that.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

.travis.yml

@@ -17,7 +17,7 @@ addons:
       - gcc-4.8
 
 env:
-  - ARCH=64 SOURCE_CHECK_ONLY=true COPTFLAGS="-O3 -flto"
+  - ARCH=64 SOURCE_CHECK_ONLY=true COPTFLAGS="-O3"
 #  - VALGRIND=0 ARCH=32 DEVELOPER=1 COMPILER=gcc TEST_GROUP=1 TEST_GROUP_COUNT=2 SOURCE_CHECK_ONLY=false
 #  - VALGRIND=0 ARCH=32 DEVELOPER=1 COMPILER=gcc TEST_GROUP=2 TEST_GROUP_COUNT=2 SOURCE_CHECK_ONLY=false
   - VALGRIND=0 ARCH=64 DEVELOPER=1 COMPILER=gcc SOURCE_CHECK_ONLY=false

.travis/build.sh

@@ -40,5 +40,8 @@ if [ "$SOURCE_CHECK_ONLY" == "false" ]; then
     echo -en 'travis_fold:end:script.3\\r'
 else
     git clone https://github.com/lightningnetwork/lightning-rfc.git
+    echo -en 'travis_fold:start:script.2\\r'
+    make -j3 > /dev/null
+    echo -en 'travis_fold:end:script.2\\r'
     make check-source BOLTDIR=lightning-rfc
 fi