ArchLinux PKGBUILD needs fixes

Actual PKGBUILD generates several errors for me. It seems be intended as a part of github repo, while usual practise is to download PKGBUILD only and let the makepkg to download needed sources. Below is version that worked for me:

# Author: mosra <mosra@centrum.cz>
pkgname=magnum-integration
pkgver=dev
pkgrel=1
pkgdesc="Integration libraries for the Magnum C++11/C++14 graphics engine"
arch=('i686' 'x86_64')
url="https://magnum.graphics"
license=('MIT')
depends=('magnum' 'bullet' 'eigen' 'glm' 'imgui-src')
makedepends=('cmake' 'ninja')
options=(!strip)
provides=('magnum-integration-git')
source=("git+https://github.com/mosra/magnum-integration") # tag: v2020.06
sha256sums=('SKIP')

# _rootdir=$startdir/../../
_rootdir=$startdir/src

build() {
    mkdir -p "build"
    cd "build"

    cmake ../$pkgname \
        -DCMAKE_BUILD_TYPE=Release \
        -DCMAKE_INSTALL_PREFIX=/usr \
        -DIMGUI_DIR=/opt/imgui \
        -DWITH_BULLET=ON \
        -DWITH_DART=OFF \
        -DWITH_EIGEN=ON \
        -DWITH_GLM=ON \
        -DWITH_IMGUI=ON \
        -DBUILD_TESTS=OFF \
        -DBUILD_GL_TESTS=OFF \
        -G Ninja
    ninja
}

check() {
    cd "$_rootdir/build"
    CORRADE_TEST_COLOR=ON ctest --output-on-failure
}

package() {
    cd "$_rootdir/build"
    DESTDIR="$pkgdir/" ninja install
}

However, I had to disable tests due to magnum detection fail (although I have it installed).

mosra / magnum-integration

ArchLinux PKGBUILD needs fixes #79