[TD-2688] fix: make CI use gcc 4.8 and binutils 2.26.

.travis.yml

@@ -146,7 +146,7 @@ matrix:
         branch_pattern: coverity_scan
 
   - os: linux
-    dist: xenial
+    dist: trusty
     language: c
     git:
       - depth: 1
@@ -156,8 +156,9 @@ matrix:
         packages:
           - build-essential
           - cmake
+          - binutils-2.26
     env: 
-      - DESC="xenial build"
+      - DESC="trusty/gcc-4.8 build"
 
     before_script:
       - export TZ=Asia/Harbin
@@ -168,7 +169,7 @@ matrix:
 
     script:
       - cmake .. > /dev/null
-      - make
+      - export PATH=/usr/lib/binutils-2.26/bin:$PATH && make
 
   - os: linux
     dist: bionic