Make Cmake work with debug build

Before this CL, the following failed to link:

    cd .../skia
    git fetch
    git checkout origin/master
    git clean -ffdx
    SKIA="$PWD"
    cd $(mktemp -d);
    cmake "${SKIA}/cmake" -DCMAKE_BUILD_TYPE=Debug -G Ninja
    ninja
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1757993006

Review URL: https://codereview.chromium.org/1757993006
1 file changed