Travis: Run the pre-C99 compilation test only once, with gcc

Compile without optimizations (and symbols) as an opportunity to also
check that it properly compiles under these conditions (re: force_inline issues)

.travis.yml

@@ -16,13 +16,8 @@ before_script:
 
 script:
  - ./configure --disable-dependency-tracking
- - make
- - sha512sum src/libsodium/.libs/libsodium.so > lib.sum
- - make clean
- - make CPPFLAGS='-DSODIUM_C99\(X\)='
- - sha512sum src/libsodium/.libs/libsodium.so > lib-oldc.sum
- - cmp lib.sum lib-oldc.sum
- - make clean
+ - >
+   if [ "$CC" = 'gcc' ]; then make CFLAGS='-g0' > /dev/null && cp src/libsodium/.libs/libsodium.so lib.so && make clean > /dev/null && make CFLAGS='-g0' CPPFLAGS='-DSODIUM_C99\(X\)=' > /dev/null && cp src/libsodium/.libs/libsodium.so lib-oldc.so && cmp lib.so lib-oldc.so && echo No binary changes && make clean > /dev/null ; fi
  - make distcheck
  - make distclean
  - ./configure --disable-dependency-tracking --enable-minimal