Fix Android build tooling and native globals

[JacktheRanger]

Motivation

• Make the repository buildable in this environment by aligning Gradle/AGP versions and stabilizing the Gradle JVM options and network/proxy settings.
• Fix native linker errors caused by duplicate global definitions in multiple translation units so the native libraries can link correctly.

Description

• Bumped Android Gradle Plugin to 7.4.2 and Gradle wrapper to 7.5.1, and removed legacy MaxPermSize usage; updated build.gradle and gradle/wrapper/gradle-wrapper.properties accordingly.
• Consolidated JVM/daemon settings and TLS/proxy configuration in gradle.properties to set org.gradle.jvmargs, org.gradle.java.home and systemProp.* for consistent dependency resolution behind the environment proxy and with a trusted cacerts.
• Fixed a CMake preprocessor macro quoting issue in libflasher/src/main/cpp/CMakeLists.txt for getlocaledecpoint.
• Resolved duplicate native symbol/linker errors by changing global JNI variables to extern in headers and adding a single definition in the respective C translation unit for libflasher, libmfkey, and libnfc (headers and tools.c modifications).

Testing

• Ran ./gradlew assembleDebug, which completed successfully (BUILD SUCCESSFUL).
• Produced debug APK at apprts/build/outputs/apk/debug/apprts-debug.apk.
• No automated unit tests were added; build artifact creation via assembleDebug is the verification performed.

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Codex Task