[bootstrap-vcpkg.sh] restore removed eval call

[Osyotr]

As suggested in #37035 (comment)
cc @SchaichAlonso

Fixes #37035
Fixes #37045

[SchaichAlonso]

LGTM (I'm not authoritative though)

[SchaichAlonso]

Giving this a second, what's the point of using a cmake arguments variable (with or without nested quotes) here in the first place?

I'm not a ninja expert, so if I want concurrent compilation, I pass --parallel to cmake --build rather then manually setting up a job pool, and --parallel has always worked for me so far. In fact it also works w/o Ninja, e.g. with Unix Makefiles or msbuild, while the job pool stuff is ninja specific.

If the job pool stuff doesn't do anything that --parallel doesn't, then the code block handling the cmake arguments and cmake invokations, namely

cmakeConfigOptions="-DCMAKE_BUILD_TYPE=Release -G 'Ninja' -DVCPKG_DEVELOPMENT_WARNINGS=OFF"

if [ "${VCPKG_MAX_CONCURRENCY}" != "" ] ; then
        cmakeConfigOptions=" $cmakeConfigOptions '-DCMAKE_JOB_POOL_COMPILE:STRING=compile' '-DCMAKE_JOB_POOL_LINK:STRING=link' '-DCMAKE_JOB_POOLS:STRING=compile=$VCPKG_MAX_CONCURRENCY;link=$VCPKG_MAX_CONCURRENCY' "
fi

(cd "$buildDir" && eval cmake "$srcDir" $cmakeConfigOptions) || exit 1
(cd "$buildDir" && cmake --build .) || exit 1

could be

(cd "$buildDir" && eval cmake "$srcDir" -DCMAKE_BUILD_TYPE=Release -G Ninja -DVCPKG_DEVELOPMENT_WARNINGS=OFF) || exit 1
(cd "$buildDir" && cmake --build . --parallel ${VCPKG_MAX_CONCURRENCY:-1}) || exit 1

where the eval statement is redundand because there's no nested quotes any more.

Further, cmake 3.13 and newer have -S and -B arguments to specify the source and the build directories, allowing to invoke cmake outside of the build directory

(eval cmake -B "$buildDir" -S "$srcDir" -DCMAKE_BUILD_TYPE=Release -G Ninja -DVCPKG_DEVELOPMENT_WARNINGS=OFF) || exit 1
(cmake --build "$buildDir" --parallel ${VCPKG_MAX_CONCURRENCY:-1}) || exit 1

Without the cd statements we can then drop the brackets, and reorder the cmake arguments to not interleave the generator into varriable definitions, to get

eval cmake -B "$buildDir" -S "$srcDir" -G Ninja -DCMAKE_BUILD_TYPE=Release -DVCPKG_DEVELOPMENT_WARNINGS=OFF || exit 1
cmake --build "$buildDir" --parallel ${VCPKG_MAX_CONCURRENCY:-1} || exit 1

---

A preset defining CMAKE_BUILD_TYPE, VCPKG_DEVELOPMENT_WARNINGS, generator and buildDir can further clean this up. Preset Files are JSON, so we don't have to bother about whitespace escaping madness if the generator ever becomes "Ninja Multi-Config". vcpkg-tool already has a preset file, it just doesn't contain a preset storing the constants passed to the only cmake invokation that the boostrap-vcpkg script ever performs.

In case the job pool stuff doesn't do just simply the same thing --parallel does... then we can configure all the job pool variables in a preset, in addition to the non-ninja-specific variables, and branch between the job pool preset and the basic preset in the shell script, instead of appending cmake args.

Getting the Prefix into vcpkg-tool will take it's time though, so go ahead with this PR.

[vicroms]

@SchaichAlonso comments aside, I'm taking this PR since it quickly fixes an issue right now.