Ninja: Prevent compilers to be silently modified

Unlike with Unix Makefiles generator modifying compiler paths was not
protected with Ninja generator.  It was possible to modify them in the
cache without the expected effect on the generated solution.  Also
activate corresponding tests with Ninja.
Remove extra slashes from LOCATION target property value

In commit v3.0.0-rc1~429^2~2 (Remove the Location member from cmTarget,
2012-10-07) a few extra slashes were added to the path construction
logic, perhaps due to a partially implemented attempt at handling the
case that GetDirectory returns an empty string.  This leads to LOCATION
paths with double slashes in some cases.  Remove them now.
VS, WINCE: Only set EntryPointSymbol for executables
Teach try_compile COPY_FILE to look for IOS app bundles.

The COPY_FILE option on try_compile never looked for IOS application
bundles. This caused it to fail if the CMAKE_MACOSX_BUNDLE was set.
Merge topic 'ninja-compiler-change'

6120fca8 Ninja: Prevent compilers to be silently modified
Merge topic 'fix-LOCATION-slashes'

92b2c618 Remove extra slashes from LOCATION target property value
Merge topic 'vs-wince-exe-entry-point'

e7aeb79f VS, WINCE: Only set EntryPointSymbol for executables
Merge topic 'fix_search_path_ios_trycompile'

55a885da Teach try_compile COPY_FILE to look for IOS app bundles.
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