Fix problem with posix_fallocate on AWS Lambda

[jedelbo]

Fixes #3193

[emanuelez]

Here are the compiler warnings:

[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/column_string_enum.cpp: In constructor 'realm::StringEnumColumn::StringEnumColumn(realm::Allocator&, realm::ref_type, realm::ref_type, bool, size_t)':
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/column_string_enum.cpp:35:53: warning: declaration of 'is_nullable' shadows a member of 'this' [-Wshadow]
[androidArm64Debug]                                     size_t column_ndx)
[androidArm64Debug]                                                      ^
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/util/file.cpp: In member function 'bool realm::util::File::prealloc_if_supported(realm::util::File::SizeType, size_t)':
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/util/file.cpp:836:1: warning: control reaches end of non-void function [-Wreturn-type]
[androidArm64Debug]  }
[androidArm64Debug]  ^
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/table_view.cpp: In member function 'void realm::TableViewBase::to_string(std::ostream&, size_t) const':
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/table_view.cpp:443:64: warning: declaration of 'limit' shadows a member of 'this' [-Wshadow]
[androidArm64Debug]  void TableViewBase::to_string(std::ostream& out, size_t limit) const
[androidArm64Debug]                                                                 ^
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/table_view.cpp: In member function 'void realm::TableViewBase::limit(realm::LimitDescriptor)':
[androidArm64Debug] /home/jenkins/workspace/realm_realm-core_PR-3195-BIPQQQ2QGOMZ2QY42PM55MCDI737SVJG2WNAIB7GASWWJTZXEZQA@3/src/realm/table_view.cpp:707:48: warning: declaration of 'limit' shadows a member of 'this' [-Wshadow]
[androidArm64Debug]  void TableViewBase::limit(LimitDescriptor limit)
[androidArm64Debug]                                                 ^